I meant more mentally what do they have in common. Some guys are pigs and simply make up an excuse to go see another girl that they think is prettier or better looking than the one they're currently seeing. I know a few people who have done this. I think before you "go out" with a guy that you "think" you like that you should get to know him more. Understand what the guy's like and what he likes to do. See if you two have anything in common or share same interests. That seems to be a good sign to great relationship. Now I assume these things are correct. I've never been in a real relationship and have ever only liked one girl in my fifteen years on this planet (I'm a guy by the way). That girl moved away and I never saw her again. But anyways I believe the key to a successful relationship is having things in common, things that both people can relate to. I wish you a great journey and hope you finally meet that special someone you've been longing for.