Virtually all activity in EVE falls within one of two categories:
1. Blowing up internet spaceships (PvP).
2. Making ISK
Generally speaking, PvP in EVE is a great way to lose ISK. At some point, every player has to come up with a way to make enough ISK in order to keep flying. There are lots of ways to do this. The method I have chosen is to station trade, and I'd like to devote this post to describe my trading approach.
If you're looking for a guide about how to maximize profits, then look elsewhere. My whole goal is to spend as little time and effort as possible, which essentially turns this into a passive source of income. I update my orders once per day, which takes between 15-30 minutes. With 1 billion ISK invested, I can expect to make 25-50 million ISK per day in profit. In terms of ISK/hr of active playing time, this is nearly as good as multi-boxing level 4 missions (or so I hear). Since I'm usually flying cheap T1 frigates and I pay for my account, this is easily enough income for the foreseeable future. If I were more ambitious, I estimate that I could probably make 150-200 mil/hr if I were to invest all my isk into the market and babysit all my orders.
Compared to most other PVE activities, station trading is ridiculously easy to get into. My station trading alt never undocks. He has maybe 3-4 weeks worth of trading skills trained, and I spent exactly zero time grinding missions to raise his corp standing in order to reduce my tax rate. Hell, I don't even have margin trading trained. Despite the perception that most people have of station trading, I have never made a single spreadsheet and have never really seen the need to. Again, my approach is not at all optimal in terms of making ISK, and I don't really care.
The skills I'd recommend are:
Broker Relations IV
Margin Trading IV
This is really just a good goal to set. I don't have all of these trained, and probably won't bother to unless I drastically need to increase my income. Wholesale IV is already overkill for the amount of trading that I do.
When looking for an item to trade, use the following criteria:
1. The profit margin between the buy and sell orders is at least 6% (ideally, greater than 10%).
2. The item has a steady volume, and is traded relatively frequently. I hate sitting on items and having unfilled buy orders. My goal is flip everything I buy within a day or two.
3. The historical median price is in between the buy and sell prices. Alternatively, the median price bounces between the buy and sell prices on a daily, or semi-regular basis. Some items may have a nice profit margin listed, but has all the trade activity occurring on one end of the margin (rigs tend to fall into this category). You want to avoid those items.
4. The value of the market is high enough to make trading worth your time. This obviously depends on how much capital you have invested. More specifically, I look at the profit margin multiplied by the daily volume. I typically try to invest anywhere from 2-5% of my capital into one particular trade.
Before you ask: no, I will not tell you what items I trade, nor will I tell you where my station trading alt operates. You'll have to figure this part out yourself.
Once you have identified an item, go ahead and place a buy order. I generally do not place a buy order for more than 10-20% of the total daily volume. This is because I want my orders to close quickly, and my inventory to move fast. I also don't want my own orders to influence the market value too much. Also, don't try searching the market for the "best" item with the largest profit margin. This is a waste of time! As soon as you see an item that fits the listed criteria, start trading it immediately.
My biggest piece of advice: DO NOT PLAY THE 0.01 ISK GAME. This is futile, unless you want to sit at your computer updating your orders for hours straight. You will want to out-bid buy orders and undercut sellers by a significant amount. This may not maximize your profit on each trade, but it WILL save a ton of frustration and make your inventory move faster.
As with anything, you'll get better at station trading the more you do it. It may be boring, but considering that both the skill requirements and the amount of time invested are minimal, I feel like this has to be the best way to make isk in EVE.