Be aware of a few things beyond the process.

If it is a piece that has been dropped from the PML, especially recently, it won't get approved. Ran into that one when I was a baby band director. Didn't know the piece had been dropped. Dick Floyd was kind enough to call me when the application arrived to let me know that. Put it away, and by the time it got rejected we had moved on.

If it is the year after a new list came out, don't count on approval. "We just put a bunch of new stuff on. Play that."

This may have changed, but the committee meets at TMEA, so you'd better be preparing your backup in case it gets rejected. With online possibilities now, this timeline may have moved up, but still have a backup. I'm old, it has been a while since I asked for a substitution, and I really don't care what the process is now...