A good idea is to visit a fish store and see what catches your eye. Don't buy yet, but jot down the names of the fish you like. Then come back here and post them, and people can give you an idea of which on your list would be compatible with one another and work for your size tank.
Don't trust what the fish store people tell you, and don't buy anything until you have researched compatibility (or asked about it here).
Do you know about cycling a new tank? If you are a beginner to fishkeeping you will need to make sure you know how to cycle BEFORE you buy your fish. People can explain it very well here, and there are also articles and old threads on the subject. Failing to cycle is the most common reason for fish death in new tanks. Again, don't listen to what the fish store tells you. They will try to sell you a bunch of stuff that will only make the process harder on you and your fish.
Also, check out the sticky at the top of the "Getting Started" page of this forum called "What fish should you get." There is lots of good information there to help you choose.
Good luck, and keep asking questions! Welcome to AA!