If you're scouting for a casual but also on-trend look, make a black crew-neck t-shirt and grey plaid chinos your outfit choice. Let your sartorial savvy truly shine by finishing off your outfit with a pair of black suede sandals. Undoubtedly, it's easier to work through a warm hot weather afternoon in a light and breezy outfit such as this one. If you often wonder how to dress as a 20-year-old guy, this combination is a real lifesaver.