I gotta say go with classic - but keep it bright.

Bright or deep colors photograph better than white and khaki. Pick a color that looks good on you, and keep the patterns subtle
(ask mom or a trusted female friend what a good color is for you, they will have no trouble.)

Styles vs. Trendy - Polos and button downs make mom happy, and will say in years to come "fashion savvy" better than the low-ridin jeans, or Aeropostale tee, believe me!
(Ask my brother about his Farrah Fawcett t-shirt picture!)

Remember you don't have to wear all short sleeves in the summer - you want a couple long sleeve choices.

Jeans - are great. Darker will photograph better, but if you have some really cool, moderately torn ones, that could work. Your pants won't show as much as your shirts, so don't stress with those. Shorts can be good - sock tans... tough to cover up.

Accessories - a cool cap, jacket, shades - these could be cool. But a belt is a necessity - it'll probably show, so have a nice one.

What about YOU?

Probably up for Most Athletic (or wish you were)?  Bring a sports jersey, maybe a ball or bat! We could work in a location shot at the field. For lots of guys this is a huge part of who they are right now, and something to celebrate, and remember in your portraits.

Love your car? Whether its a muddy jeep, cool truck, or sleek sports car, we can work with getting your ride in your photos. Unless it's a muddy jeep (and that's your statement) you ought to wash it.

Play guitar or other instrument? We can work it in if you like, in a cool way - not the school band photo pose...        
            eeek!

Hair, Shoes - Other Stuff

Hair - If you need a haircut, get one at least the week before your session. You probably ought to wash it to make mom like the photos more...Don't get that mohawk before I get to do your portraits; see the "class" statement above. If you are prone to - don't get a perm (ask my brother, I think it was the same portrait as the Farrah Fawcett tee! If I could find that for Facebook...)

Shoes - They probably won't show that much, don't stress over them. We may be in a creek in some shots - can you take them off?

Other stuff - Don't worry if you break out right before the session - that is what retouching is for. Shave if you need to!