Personally I like Stuff from Firetrap, Diesel, D & G, Full Circle and All Saints mostly.
I find most of the simple/plain stuff from H & M seems to fit pretty well and hang right on me and be cheap as chips. Flashy belt buckles seem to give girls an excuse to check out the package which is usually a good thing.
As a general rule I think...either have a loud/flash shirt OR loud/flash jeans... never both at the same time. It pretty much always screams 'Try hard'. And you will have to 'try hard' to prove to randoms that you aren't a cunt. Then again some girl's go for the whole 'cunt look' so each to their own i guess.
Oh and I love charity shopping...it's a great way to find random weird interesting bits of clothing that no one else will have.
Oh and I'd say anyone with any game/banter at all should avoid those lame slogan t-shirts. I think they are for people that lack the ability to start conversations off their own bat. I always cringe when I see people out on the pull in that shit I always think 'make your own fucking joke dickhead!'