This is the section with a bunch of articles which you can check through for some good info.
Articles - Aquarium Advice
The most useful article to read first is here (also in my signature because it is that important for a good foundation for fish keeping).
Guide to Starting a Freshwater Aquarium - Aquarium Advice
As for which fish to get I would visit a few fish stores, mainly if possible stores which are not big box stores. And just observe and take notes on some of the ones which really seem to interest you most.
You can compare fish sizes and compatibility, tank and water needs to get the best matches. Also AQadvisor . com can be helpful.
Edited:
And never jump into buying something. Research and get a knowledge of how big and what kind of care the fish need and if they would be right for your tank.
Common plecostomus get to 18 inches long, Comet/feeder and common Goldfish do too.
Just do a search online for worst fish for an aquarium and start seeing that half the fish in sold at Walmart are on the list, as well as the majority of big box stores stock a large number of fish which are not even good for the starter tank or any aquarium tank.
Unbelievable stores sell Red Tail Catfish which can get to 5 feet long and are 150 lb in the natural environment and Colombian aka Silver Tip Shark, Bala Shark and Clown Loaches get about a foot (12 inches) or longer, and like to be kept in groups.
Lots of fish should be kept in groups. Also important for the fish to behave better.
Many fish need different water temps and as mentioned tank conditions to be most healthy.
It is really great to see you getting as much info as you can to have the best chance for a successful tank!