Important, before I begin: This guide is based upon my personal opinion and experience, it might differ a bit from reality or your opinion, but then again this is what every player made guide is like.
Things id like to talk about:
Ways of making money,
My opinion and approximate amount of profit/risk.
2 Mining
Mining is both the most common, and oldest form of making money. It basically means getting a frigate, cruiser or battleship. and fitting mining lasers on them. Mining is done frequently by having a few miners in asteroid belts (which are found in nearly every system) fill up cans, and then have industrial class ships pick up the ore left in the "jettison cans", this can also be done in secure cans, however they only anchor in less secure systems. The reason secure cans are being used is because of the fear of so called Ore thief's, They're people in industrial ships that will come to your cans and take the stuff in them, they cannot be shot or they will trigger concord (=police) response. Usually the best mining ships are the ships with most gun slots (=most miners). frigates: The race here doesn't matter, usually frigate pilots will mine solo, therefore cargohold would be nice to have. for example, bantam, probe, imicus.
Cruiser: If you have time and money to spare for the skill I'd recommend getting the thorax, this ships got 2000 m3 drone space and 5 turret slots, so defence and mining capability are at its best with drones and 5 lasers here, a vexor or maller would be second choice, below that most ships will have near equal mining ability.
Battleships: Most battleships have enough turret slots to be a pretty good miner (tempest and domi = 6, arma and mega = 7, apoc = 8 ) drone bays on these ships are all fairly enough to keep defence at nominal levels. The best ship is of course the apoc, but the 1 or 2 more slots its got only insure a 12.5 or 25% higher yield, which with skills isn't that much of a difference (especially if its the first battleship I would recommend the Armageddon since its half the price).
Mining can of course be done in different areas, I consider: 1.0 - 0.9, 0.8 - 0.5, 0.4 - 0.1, 0.0. of course location also means what minerals are available, but I will keep it general (in practical terms one or 2 minerals will be missing in each area because of the location/region the belt is located) (profits are considering 1 Indy and 1 battleship, solo).
1.0 - 0.9: These are some of the worst areas to mine in, these are often very close to general travelling routes and will be mine by hordes of people and strip-mined by mega corporations they'll contain scordite and veldspar most of the time. also there are no pirates. expect several millions per hour.
0.8 - 0.5: These belts are often mined unless you find one out of the normal routes people have, I found a few totally unmined, this can be profitable. Common minerals are veldspar, pyrox, scordite, plagio, and in the lower security levels also omber (0.7) and kernite (0.5). Expect a few frigate pirates, but nothing drones cant handle. Also player pirates are not to be found in these sectors. Profits are again several millions per hour, yet more then 0.9 and 1.0, but at a slightly higher risk.
0.4 - 0.1: STAY OUT OF HERE unless in rather large groups, in my opinion this is the domain of the real player pirates, expect to find descent ore, cruiser NPC pirates, but worst of all player pirates, these are people usually working in groups of 3 or so, they will first come in with one of them, he will scan you, by this time you should already be at a station or even docked! If you plan to mine here, in any kind of group smaller then your whole corporation watch local with your life. Profit can be around 2 - 3 mil per hour per person if its mined correctly. However against the risks I suggest going back to 0.5 - 0.8 for more profit. or if you know how to run properly you can stay here. There are however sentry guns at the stations so you're safe there.
0.0: lawless space, no sentries, a players will is the law here. You can be killed without any security hit. however in my experience as long as the refinery and your mining spot are close to each other there is not that much risks from player compared to immense rewards. expect 10 - 20 million per hour or sometimes even more. the NPC's are very powerful and 1 or 2 battleship sized defenders are a must (or park your own tanked battleship in a safe spot).
If you're on your own id recommend ninja mining, which basically means, get a ship that can run properly. park an Indy at a safe spot in the system, and mine in the ship until you see pirates. once you see them, run to a moon or your safe spot. Wait for about 10 minutes till your scanners clear and go back. Then once the can contains about the amount your Indy can carry get your Indy out of its safe spot and make it grab the stuff also bookmaking your mining asteroid is a good idea so you wont have to travel much.
My own favourite: 0.0 space, if you're in a good alliance, have a good group and don't have 2 many player pirates around this is the number 1 way to make money, however its only for the people with nerves of steel and people that live with the knowledge they could lose a ship daily. For anyone that does not have this and people that are simply not ready for it yet I would recommend 0.8 - 0.5, that is if you can find a descent system.
3 Agent missions
Agent missions at the moment are one of the safest and most boring way to make money. To start you need to climb up from a lvl 1 agent to a lvl 2 agent to a lvl 3 agent. This can take several days. The 3 levels all contain a different difficulty, level 1 is very easy and can with ease be done in frigates, level 2 can be done in frigates but is hard. At level 3 either a battleship or a cruiser and industrial are a must.
Of course each higher level will give bigger rewards. An agents effective quality will show the height of its rewards, this can be raised by standing and by certain social skills. (so can the standing with the connection skill by the way) I'd say agent are for people that like to watch television while playing and cant find a good belt to mine in, and for people that are starting the game and need their first frigate to cruiser and wish to do this solo.
There are 2 different classes of agents, Research and development and regular agents.
Research and development agents will only give out rare blueprints, and are based purely on luck, no matter what you do, it will always be a lottery, I myself have had an agent for nearly 180 days and still nothing, others had 3 blueprints in a row. If you manage to get a blueprint you can make several (I'm serious) billions selling these items overpriced (but heck you're nearly the only one with the print....). In my opinion its not balanced out at all because CCP bases some richness on what is nearly pure luck. id recommend people get 1 RD agent for the sake of it, but its not a reliable way of making money. Oh yeah, and to increase the amount of Research points (RP) you dot have to do anything, but by doing missions you can sometimes double or triple the daily amount (get 200 instead of 100 once).
Regular agents: They are also based on luck, and the only big profit to be made with them is by selling the basic implants (whom give a +3 to a certain attribute) for 12 - 15 million a pop. If you're lucky you can get one every 10 missions, I think the average is about 30 missions. But again this is based on pure luck, you can only get implants during important missions, which are pretty rare. You need a level 3 agent with 6.0 standing (at least) to get implants though. so dot expect to start of with them, it requires some work. The rewards per missions are around 150,000 ISK a pop, which is not much so I wouldn't go for that. There are tech 2 building components to get and sell though. I have no idea how much this can make you extra per hour but it doesn't exceed mining or NPC hunting unless you're lucky. (this is what agents are based on though). You can direct the type of missions you'll get a bit by picking the right corporations and the right part of this corp. For example, security in Caldari navy will likely get you fighting missions. however you will still get some gun shipments, so keep that Indy ready.
What I often do is have 3 level 3 agent in the same station, so I can take all 3 missions at once and complete 3 missions where others complete one.
4 NPC hunting/chaining
Quite profitable, try and take your abilities to the max because the higher the more money. The most important thing here is to know your limits, don't try to take on spawns that are a lot higher then your own ship and ability, if you get killed this will ruin your profits for some time. Its better to take pirates a bit below your ability then take them to high, also chaining will mean they'll instantly respawn, if you had any difficulty in the original spawn that problem might get duplicated when they spawn right after they die.
Commonly chaining is the best way for making money, however some voices say this will be removed in the future, still I will discuss the basics: First you skim through belts trying to find one that suits your own power, then you'll have to kill the entire spawn except for one pirate, this should be the weakest one, let him attack you constantly and don't let him get away. At first nothing will happen but after some time (can be anything from 5 minutes to an hour for the first respawn) the whole spawn will respawn, again you kill all but the one circling you, then after that it should respawn faster and faster and faster, until it will be nearly instant (right after you kill one he'll be back).
You need to experiment for yourself what chains suit you, and sometimes you will have to learn the painful way, but eventually you'll get good at it, or ask corpmates for advice about your abilities.
Another way would be going to a base, this is hard at first because there can be up to 30 pirates at once, but there usually only a few spawn points, and them spamming one at a time at a slow rate (this rate cannot be increased).
The biggest prize often comes in the loot cans the ships drop, but can also be their bounties, usually you alone will be enough to chain, unless you're going to chain battleship pirates (0.0 space) then you might need a group, I would also recommend shield transfer arrays for everyone in this case (with 4 medium arrays at one ship hell be invincible compared to the enemies, even if its the heaviest NPC battleships). Profits killing NPC's battleships aren't that high because of the group split, but sometimes the loot is very rewarding. NPC hunting is profitable but it is risky and knowing your own limits its a must.
exploits: I wouldn't call it an exploit but officially chaining is one, can't get banned for it though. Another one is when fighting heavy Gurista's, hide behind an asteroid, since they're using missiles the missiles will not hit you, and since Gurista's like blasters, a big rock can hold them far enough not to use them.
5 Trade runs
A friend of mine used to make 100s of mils a day with them, but now that's no longer possible, its useful for noobs but I wouldn't suggest doing it if your any kind of age, I haven't done any recently myself and if anyone can send me some trade runs to prove me wrong ill reward this with a small ISK donation, ill also expand this part of the tutorial if I get more info. ... until that time I cant really tell much about trade runs because I lack recent experience, I can however explain the basics.
You need an Indy or another ship with descent cargo, find a place where something is sold cheap, then try sell it at a higher price somewhere else, it requires a lot of planning and research and is therefore time-intensive to start with. but there is the autopilot once that's all done.
"exploits ": This used to be a famous one, put up a large sell order for a "low" price, and a buy order (with an alt) somewhere else (a bit far out) once someone bought the stuff cancel the buy order and the money is all yours. ... this is harder nowadays though, and finding an item suited for this is hard on its own.
6 Pirating/Scamming, and everything else god has forbidden
This generally means letting other people make money, and you take it away from them the "easy" way, this includes scamming, pirating, gate camping, etc.
6.1 Scamming
One of my personal favourites. I'm not going to go into details about how I do it, but lets say I didn't exactly mine for that raven of mine. This basically means using the stupidity of others, I will tell you people some old scams though so you might think of your own way. Selling shuttles for 10 million a piece, selling minerals for ridiculous prices, putting a condor named scorpion in the trade window (they used to look a like), etc.
Scamming is commonly done with alts, but this no longer works because people know alts are being used and won't buy from them nowadays. Scammers can however expect to become outcasts and can expect to no longer be appreciated if this gets known to others. It can definitely be the most profitable thing to do, but it will get you on more blacklists then pirating itself will.
6.2 Ore theft
Now I have to admit prior to making this guide I wanted to know what it was like, so I trained an alt to fly a small basic Indy, within 2 days I was on the KOS (kill on sight) lists of at least 3 alliances. This is the most hated profession in the game, it makes about twice the profit mining normally does. You just basically get an Indy, sit in 0.5 and grab the unsecured cans of poor miners (they can't attack without police response as of yet). Sometimes they will attack you, with a nice explosion as a reward.
6.3 Pirating
Now the real forms of pirating would of course be killing miners/NPC hunters and camping gates, most people see pirates attacking alliances, but I consider these people to be space Vikings not real pirates (m0o for instance). This profession can be among the most profitable around, if you're lucky (and any good) you can have people ejecting from their battleships to save their pods, and you can collect an easy 30 million from most smart pilots that desire to live. Unlike what most people think pirating is commonly done in 0.1 - 0.4, not 0.0, 0.0 is usually filled with groups of people, this usually ends up in a fleet battle, and not a fast miner hold-up. To start the way of pirating described here you used to only need a blackbird, but since the nerve you need is a little more, you also need to make sure friends are not to close, and you need to put pressure on people. However blowing them up is not much profit so negotiation is a must.
6.4 Corp Theft
Among these are the most famous, hated and richest people in eve. It means betraying friends you've been with for months, and often means being hunted till the end of the world. Some examples of these are agent shield (who corpthieve after his corp. let a corpthief join, dual corptheft). and Fallzone (who stole form the richest corporation at the time).
This is a profession most hated and it will not get you friends, even among pirates. But it will get you immense wealth, after which you can sell your account...