OK I'm looking for good way to build up my credits but I can't find any. I've played for over twenty hours and have not found any missions that give me credits. Can any one give me some suggestions as to how to increase my bank account?
Sell everything you get that you aren't going to use. You can make credits very easily. You WILL NOT earn credits through missions at all.
Do NOT do any missions which require you to "aid the planet" because that will cost you credits that you won't get back.
If you have a nice item of uncommon, rare or very rare status, you can list it on the exchange for a price of % of its value and make more money that way if: A) it sells, B) you don't list it for too much.
If you see people listing things for huge amounts of money, those are the same people who have had things listed there since before this game was released. Price your wares accordingly.
At no time will you really need credits. Everything you will ever need you will get through mission drops and mission rewards. You won't believe that now, but the first time you spend $40,000 credits on a new deflector array and then get the same one as a mission drop right after, you'll know I was right. And if you want to buy a ship - you'll get a free one every time you reach your next level. Plan for that.