Get to know your horn
It's late, so here I'll keep it short for now. Your goal as a trumpet player is to eventually become "one" with your trumpet so that you can make any sound that you can imagine actually come out the bell. There are two steps involved. First, you must have a concept of what you want to come out of the bell. This comes from extensive listening to great players. Then you must actually execute what you imagine, which requires have a deep understanding of you horn. The best way to really get to that point is to improvise. Just make stuff up. At first what you want to play and what actually comes out of the horn will probably be fairly different, but it will get better. Besides the obvious benefit of eventually being able to play whatever you want, you will find that almost all other aspects of your playing improve.