I play PC games exclusively, and I get most of the info from gaming sites such as gamespot, ign, gamespy etc. I use their reviews as a rough guide, and make a final buying decision based on a) game demos, and b) information found in forums; i trust real user reviews more than the magazines or sites. Real user reviews tend to highlight flaws in the game that may not matter for the 'professional' reviewers, but can make or break a game for me (eg. the lousy control system in Deadspace).
Some of the bigger name games, I'll buy without waiting for the reviews - COD series, Oblivion/Fallout etc.