What can my guy friend wear to impress a girl?

My friend is a guy and he likes my other friend. ( whos a girl). He wants to impress her and thinks he has tried everything. How can he impress her style wise? He needs an idea on what to wear. can someone help??

Personally, If a guy dresses nice and clean then its a turn on. I love something like an abercrombie tee, with a nice pair of jeans or shorts.
good luck!