I think it primarily depends on the style you're shooting for. English varieties for english beers, american(ized) hops for american styles, german for german, etc. That said, I don't think there any rules about what can be paired with what.
I can't find it online, but there's a cool hop wheel/chart that's in "Brewing Classic Styles" by Zainasheff to see where each of the hop varieties lands as far as citrus/spicy/herbal/evergreen/etc.