Depends on his body build, but what always gets me is a button down and jeans with converses or just regular tennis shoes. I can tell when my boyfriend wants something because he'll go all out and it isn't something he normally wears.
I HATE HATE HATE guys in tight pants. Black dickeys and jeans are what guys look good in to me. I don't really like shorts unless their swimming or working out wither. Kind of tight but not ridiculously tight shirts are really hot. And personally, I like aviator sun glasses
Baggy jeans and a tight shirt, that way you can see his muscles...mmm...
Definitely tight t shirts. Those are a must. (But only if you're in good shape, tight tshirts on overweight guys look ickyy) For pants, definitely not tight, but not super baggy that just looks stupid. Go for ones that FIT. (Not too short either that looks geeky).
I like to see my guy in really comfy casual clothes around the house, it's really sexy to see him in like pajama pants, or really soft comfy shorts or something. I don't know why it's just sexy.
Most guys look super hot in aviators. Sneakers are good, but they can't be geeky looking. Guys for the most part look really sexy in Timberland boots.
And boxers/boxer briefs/ and whitie tighties are all super sexy to me. But for the second two, they can't be too big or else it just looks silly.