The guy seeks your company and starts making excuses to be near you, looking for reasons to talk to you either in person or in other ways (phone, messaging, etc.). When you're together in the same room he's looking at you even if not necessary. When making a list he would often start with you.
If you're lucky and he's quite the gentleman, he's also usually more considerate than the accepted norm, bit some guys are overcome by their embarrassment, and might actually act more shy than usual.