Listen
A lot of time when we speak, we are constantly trying to fill silence to keep things from getting awkward. Instead of babbling on about nothing, listen to your talking partner. If both parties are listening and responding conversation will come much more naturally.
Keep up with current events
Keeping up with the news is great way to have things to talk about all of the time. You don't need to have big deep political discussions or anything like that, but it's a good way to have some topics to bring up if the conversation comes to a halt.
Look for common ground
If you find something that you have in common with the person you are talking to, the conversation will go much smoother. You'll be able to talk for ages if you find out that you both share the same movie or love the same restaurant. Maybe you even have a shared hatred of something with that person. Even people who are complete opposites will have something in common.