I always buy my games from the secondhand bin at Game. Have about 17 now and have never paid more than £5 each
Favourite game at the moment is Gun Metal.
As long as you dont get into the mentality of 'got to have the latest title NOW!!' then you can make massive savings!
Ive also got about 18 playstation 2 games this way and I dont even have a console yet! (Second hand PS2's are £99 in Game which is way too high.)