If the time says 2 minutes or 20 seconds, use it all. The high master shooters in my league use all available time. Another thing was not to push on the barricade, since that leads to poor shot placement on the target.
Don't think too much or make last minute equipment checks, and be alone when you load magazines or need some prep time. To some folks that may seem like you are rude or unsociable, but there is plenty of time for that after the match.
Probably the most important, concentrate, front sight, front sight, etc.