There's another thread a lot like this one
here and some of the information there might help you out.
The best wayto learn how to play RPGs is to have someone there to show you. The game store group is nice, or a friend is better. Without some of those resources, you might try joining one of those play-by-post message boards to get in the spirit of telling stories with each other.
The tricky part of tabletop RPGs may be the rules. You should look for a game that is light on rules rather than an encyclopedia to try to read through. I have some personal preferences as to games, but one to try might be
Spirit of the Century because it's pretty narritive (rather than number crunchy) and is the core rules which the
Dresden Files RPG are being built upon.
Often, early versions of games are more simple than newer versions becasue as people play the games they add to them and the game slowly expands. If you want an "old school" game you might look for any
Dungeons & Dragons rules set publlished before 1999, or
Tunnels & Trolls of 5th edition or earlier. Both are simple enough to figure out by yourself. These can often be found cheap on e-bay. I can give you more exact titles to search for if you have interest in these products.
Another option is to search google for "RPG" and "free" and find some stuff that won't cost you anything to read over. The downside of this is that the quality control doesn't exist and you may end up more confused than you began. Some free RPGs are better than others, however, and you might look for
Fudge or
Fate, both of which are excellent games.
Tabletop RPGs are all about story telling with each other, and the rules just help us avoid the "did so / did not" arguments. If you find the right game for your personality, you should find RPGs to be an excellent hobby.