You might want to look at some of the species profiles - with a 10g you're limited to fairly small fish by the size of the tank.
I think many people start by choosing fish they think are visually appealing, or fish with personalities that appeal to them (some like calm, peaceful fish, others like predators). Some like a centrepiece fish (for example a betta or dwarf gourami in a small tank, or an oscar or other large cichlid in a larger tank) with or without a few other fish. Others like to keep only one species or similar species (for example an African cichlid tank), and some people like a mixed community tank of different kinds of fish that inhabit all the levels of the tank and get along with each other.
I discovered what I like through years of trial and error. I've kept MANY kinds of fish (at one point I had seven tanks) and realized that my tastes are pretty simple - I like brightly coloured, smallish fish that aren't overly demanding and get along with each other. I do have one centrepiece fish (a nearly solid white angel) in my 45g community, who I'm very attached to, but he wasn't planned, I just saw him alone in his tank at the store, knew I had a tank where he'd be happy and that was large enough, and voila. Sometimes we don't choose them, they choose us!
Do some research to make sure the fish you choose are appropriate for a small tank, but other than that it's all about what YOU like.