First Date : To a woman, the effort you put into your clothes for a date indicates how interested you are in her.
As always, you can't go wrong with a collared shirt, such as what Mr. Pitt is wearing. Not tucked in, and not buttoned all the way up. Go with jeans down below to keep it relaxed and less formal. You have some flexibility with shoes depending on how formal your top is - skater shoes, loafers or sandals could all be fine.
Since you will presumably be spending time looking at each other "up close and personal", you will want to give your Grooming (finger nails) and Accessories (wallet, watch) some extra thought.
More tips found in Shoes, Pants, and General Fashion Theory
More event-specific tips: Beach, Formal Occassions and Clubbing
[Events]
"The soul of this man is in his clothes."
William Shakespeare