The full week before competition, we begin every practice like competition warm-ups. This helps a lot! We compete UCA school comps, so every competition warm-up is different. I always contact the person running it to find out the set up of the warm-up room. Some are multiple mat stations with x amount of time on each. Some are like nationals with a full floor for x minutes. We never waste time in the warm-up room stretching, kicking or jumping. We do that before we go into the room, so that as soon as we step on a mat, we are ready to go. Part of practicing warm-up rotations includes them knowing what groups go first, which tumblers go first, how to fit all of us on 2 strips to warm-up standing, etc.
Don't over do it either and wear them out. Sometimes the competition will give you an insane amount of time on the mats. One comp last year, we did what we needed to do and then talked in a huddle the rest of the time. I know the guy working the mat thought we were crazy, but we did our job for our warm-up and didn't need the extra 8 minutes we still had left on that mat.