Any musician has to be able to balance out their practice time to really get the most out of that particular session. When it comes to playing the trumpet this is essential. As well as being a highly creative task, to play the trumpet is also a highly physical one. Many authors on the subject have compared trumpet playing to being an athlete.

First off, the warm up is essential. No warm up could damage the chops and lead to days of troubled frustrating playing. It doesn't have to take hours (it's a very personal thing), just some long tones, flexibility and tonguing to get the blood flowing and all the elements engaged. From this you can introduce some more strenuous exercises. Maybe tailoring it to an aspect of playing that you feel is a weak area or going over a range of techniques to keep them in check. One of my favourite books for this is by the trumpeter Frits Damrow, Fitness for Brass. And of course the Arban as a standard text for all brass really. 

I also believe it is important to have a study on the go at all times, the 14 Arban studies being a great starting point. Studies will improve many aspects of technique, as more often than not they are tailored toward something specific. But the biggest benefit is that you must always think musically. With an exercise it can occasionally become somewhat mechanical, but with a study you must still create a piece of music. Transposition can also be worked into this part of the practice too.

Then of course students should always have a piece of music that they are working on, be it a concerto with an orchestra or a new lead sheet.  We learn to play so we can create music and be expressive, so don't get bogged down with exercises. Always think about the music and put yourself into it no matter what you do or what style you're playing in.

And most importantly sing: sing the notes without the trumpet and when you play the horn sing through it, enjoy the creative process.