For anything such as Games or Music I check out Amazon to see if they have it. Usually you can get a strong impression from the reviews, usually customer reviews, good or bad, put together have enough information for me to make an opinion.
Other than that it's usually what comes up in conversation amongst my roleplaying group, Republic Commando is currently the topic.
That or this Forum. What will swing me to buy a game is what I've read about it and after playing the Demo.