You can't tell by looking in someone's eyes if they will settle down. That is really a fantasy approach and has nothing to do with reality.
In order to know if the person will settle down you must get to know the person intimately first. A man has to want to settle down with you in order for it to happen. If he marries you out of obligation because he thinks that's what you want, both of you will be very unhappy.
You have to take chances to get to know the guy. There is no magic trick or quick pick. A guy will be a playboy today because he hasn't met the one he wants to settle down with, and tomorrow he meets her and gives that all up for love. He may start out not knowing if he wants to settle down but getting to know you and fall in love with you might make him realize he wants to spend the rest of his life with you.