The process, as I understand it, is to get a day job to pay the bills. One of the bills should be something like Unreal Tournament, for which you can make your own maps, bots, skins, weapons, vehicles, etc. Upload to net, get feedback from players, tweak map, repeat. This gives you experience not only with the tools, but with actual players. Should give you a leg up over the competition.
If shooters aren't your style, there are other options, like making an Ultima-style game with Exult.
http://exult.sourceforge.net/