Ok from my experience, stick with really impressionistic flies(wooly bugger, charlie, gotcha etc.). Some more carp specific flies out there are Carp Crack by roughfisher, carp candy by a guy named mike I think, and both guy's have blogs so you can check out the other patterns. Its more about presentation than fly selection. I almost always start out with a crazy charlie sz 8-10 in tan. This is typically a successful pattern for me. Some people fish much larger patterns like 2-6, but I think that is dependent on the size of carp you are targetting. I am not fishing over 50lbers, so I go a little smaller. Once again, stalking the fish properly, targeting active feeding fish and delivering a nice presentation is 90% of the game, so dont fret too much over fly selection. Check out some of the carp blogs, they will give more insight on flies than I just did.