You pretty much have to find out what 3D engine the game in question uses, what file types the model files are stored in, and then find a pluggin for maya that converts a .mb to that file so it can be imported into the game.
I regularly convert .mb files to .ase files for use in the Unreal engine. There is a pluggin that does this for me, so all I need do is make the model and use the pluggin.
If you have a certain game in mind then go hunting around the games website, if there is any forums for the game go hunt there. And absorb as much infomation as possible.