When Seth Sanchez and I went through the Power Player Trumpet Course together, one of the things that made the fastest difference was doing lip squeaks.
Jordan calls it the top-down approach. Using a lip squeak will let you hit notes way higher than your normal range right away. In his course he shows you exactly how to do it so you feel confident squeaking out double high C's even if you've never played that high, and then actually playing those notes on your trumpet.
I made a few short videos of the two of us practicing our squeaks.