Manyard and others have said that one key to playing high is to take a tune and play it up an actave focusing on playing the piece musically. Well, I have discovered a website of some very simple "familiar" tunes that would allow me to do this and I thought others might like it as well. The simplicity allows me to focus on what I need to do physically and the tunes themselves allow me to hear the note in my head before I play which is also important. Hope this is useful.
Up an octave would just be pusing my playable range which I think is a nice intermediate step.
Free sheet music - Easy trumpet