Eye contact. Obviously you don't want to stare but eye contact is the best way to establish yourself as a confident and thoughtful person. I might glance at her lips from time to time, especially when I'm interested in going in for a kiss, but other then that, eye contact!
i.e. for all you guys out there... If she is cutting eye contact to glance at your lips, and repeatedly does it, chances are she wants a kiss; just a tip.