There's no way of telling this during sex. It's what he does after and before. You can find clues about a guy's intentions before you sleep with him. Does he immediately start hitting on you when you meet him or soon after? Or does he take his time and get to know you? Is he jealous when other guys pay attention to you? Or he doesn't care? Is he interested in your personality, or your looks and having fun?
After sex, is he quickly out the door? Does he call you again?
You can't... Everyone likes different things in sex, doesn't mean that there's anyone way of telling if something means he cares about you. If he cares about you you can tell from other things sex is not a good way of measuring it at all.
The only way I would say you might be able to tell is what he does after sex. Does he immediately roll over and fall asleep? Get dressed and leave? If so he probably just wanted sex.
While there's no tell-tale signs, a guy who is generally really into you will stop (or at least slow down) to kiss you. He'll hold your hand and maintain an extended eye contact. I noticed that guys who really are just interested in a hookup will only have sex... no romantic gestures or anything. Not so fun...
And if the man initiates spooning (snuggling) it means he cares for you.