What Should Men Wear on a First Date.
First date attire will depend on the location of the first date. A black suit at an outdoor concert will not win you any points! In general, if you will be going to dinner in a nicer restaurant, meeting important people in her life, or appearing at a business function, a suit or dressy casual are always good choices. A navy blazer, khaki pants, and a blue shirt is a classic preppy look. Do a little investigation, and make your clothing choices based on facts.
If the occasion is definitely casual, you will still want to err on the side of moderation for a first date. Khaki pants or your best jeans, a collared shirt, and an optional sport coat are all good choices. (After all, she might get cold and you could offer her your coat!