Well, first port of call used to be GS, until the Gerstmann business, since when I have found no particular replacement. After GS I'll hit up Metacritic and basically click on any link that looked interesting - whether to IGN or to some random print newspaper, doesn't matter. If the score is different from the majority, I'll check it. If the writing catches my eye in the preview, I'll check it. If neither occurs, I'll usually pick an internet-readable review at random and away.