Most Helpful Guy
Guys hold their physique in a high reguard so if he looks pretty muscular maybe mention it. I feel like guys and girl should have equal opportunity to ask someone out at the gym because you never know when you'll see them again. Then you miss a potentially great opportunity.
Most Helpful Girl
Make friends with the person first. A gym is no place to be asking somebody out on a date. And it can distract others who are trying to workout. You don't want to get involved with the wrong kind of person because your falling for the looks, etc. Anybody can ask anybody for a date. But at the gym, and in that situation, it's not a smart idea. And if you're rejected it can get very awkward. Plus you don't want to date a stranger.