With tinny blasts on tiny trumpets
The title of this entry is a portion of one of my favorite quotes (see below) by cartoonist Walt Kelly.
Of course, this is not at all how I think of the trumpet, but it got you to read this far. Mission accomplished.
There are a few basic ways I view the trumpet in the brass ensemble: treble clef workhorse, brilliance, and color. I think the workhorse and brilliance comments may speak for themselves. Other than mutes and the expected glorious trumpet sound, color variation in the trumpet section is primarily derived through use of the piccolo trumpet or the flugelhorn.
I enter the soprano line in the Trumpet 2 stave of my template. And then I'll start moving things around - this is the fun part. I like to make certain of a couple of basic things (for all voices really) - everyone in the group is musically vested in the outcome, and that I don't beat up any one player too much. I'll look for places where I absolutely want a flugelhorn sound which will affect all other parts as well, and where I want the entire piece to "top out." This will determine whether the piccolo is necessary or not - for pitches not color. I may decide to use piccolo anyway, even though the range of the piece doesn't absolutely demand it.
Inconveniently, composers rarely confine the overall range of their composition to the range of a brass ensemble. That means compromise and hopefully crafty solutions at both ends of the pitch spectrum. Sometimes, I'll find myself writing in a register that is just going to end badly and have to rethink the entire passage.
Not all soprano voice material is going to stay in the trumpet parts. When it's all done, the trumpets will have plenty to do, so I will always look for ways to move the sound 'down' in the ensemble. This may even mean writing an entire passage for low(er) brass an octave lower than intended by the composer. This can serve to add variety to source material that is very treble oriented. Also, writing music in the highest tessitura of an instrument can suggest to the ear that the music is higher than the actual pitch (e.g. middle c sounds "high" on the tuba, but "low" on the trumpet). I'll sometimes use pitched percussion instruments (xylophone or glockenspiel) to suggest something is higher than it is, as well as adding some crispness or sparkle (respectively) to the sound.
Other than that, there's not much magic to report. I just prefer that the trumpet players still like me at the end of a performance.
"There is no need to sally forth, for it remains true that those things which make us human are, curiously enough, always close at hand. Resolve then, that on this very ground, with small flags waving and tinny blast on tiny trumpets, we shall meet the enemy, and not only may he be ours, he may be us." Walt Kelly, from the introduction to the Pogo Papers