Your players and my niece have something in common.... they all have needs and often have trouble communicating those needs.
Players, and therefore their characters, have different drives. Some want to level, some want to roleplay, other's want to acquire magic, or fame, or power... or more then one of these, or none of these. You need to understand your players' needs for them, and you, to get the most out of the game.
Play with the same players long enough, you'll learn what drives them, but a good player will communicate what drives them to their GM. A good GM should be able to read those needs and drives without much help.
My 3 1/2 month old niece has been trying to communicate with me tonight, and she's not hungry, doesn't need changing, isn't ready to sleep - I'm going to vote "she's got gas", but it will be a lot easier when she can tell me exactly what she wants. In the meantime, she's very frustrated and upset. I'd hate for your players to feel the same way ;)
Some new house rules & additions - As a way of procrastinating from doing more work on the adventure-campaign book I've been working on seemingly forever I decided to collect my miscellane...
41 minutes ago