I never thought about this before but you can make more money by refining some of your loot instead of selling it! This is done by calculating the sell price of each mineral that is used in the items. If this number is greater than the best buy offer for the item, reprocess that item and sell the minerals instead!
There's a great program (only for Windows) called EveRefinery that can help you make the choice between reprocessing and selling your items. The only thing I don't like is the choice of colouring; there's usually a lot of red and green rows and it's just too bright heh. Otherwise it works well and I've made a little more ISK than I would have before using the program. Every ISK helps!
There's a website for loot refining made by Eve Online Market Guide. You only have to supply a limited-access (asset listing permission required) API key. I haven't used this tool so I don't know how reputable it is, but with a limited-access API key they can't do any damage to your account, so why not try it.
EVE Mentat is a trading tool for Eve. You can view all your wallet transactions, orders and market data in a single location and compare them much more easily across regions. While in EVE, use different characters in different regions and click "Export to file" for each item in the market. Then in EVE Mentat, import the market data from those files. EVE Mentat will tell you if your order prices are unprofitable and it will make it easy to compare which regions have the best buy/sell prices for items.
EVEMon is used for skill planning and making sure your character is training up the skills you need. It helps also because you can tell when you need to login and setup a new skill training queue. It can give you a listing of future skills that you have to train as well.
Python Fitting Assistant is a tool for helping you pick the best items to fit to your ship. It will even factor in your skill levels to give you a more accurate analysis of your ship fittings. Use it with the market data tools to find the best prices for items, and find out which skills you need to train up to get the most out of your ship.