Lips buzzing

Buzzing with your lips alone without instrument or mouthpiece will improve your tone and strengthen your embouchure. It may also solve some embouchure position problems.

To get a nice buzz, bring your upper lip slightly on top of the lower one and blow some air. With a bit of practice, you can control the pitch of your buzz. 

I often practice buzzing a few simple exercises ( just a couple of intervals) which I repeat on my mouthpiece and then on the horn. The tone is instantly richer and more focused. 

Here is a little example. It's very simple.