Great thread with outstanding info. I wanted to add a few others:
* Pay attention to the weights used in the warm-up area compared to the lifting platform. A sanctioned meet will use the same weights. This is mega-important. If the weight feels heavy in the warm-up area, adjust your opener. Most commercial gyms are notorious for underweighted plates.
* If you normally train in the evening (like most of us do) get up a tad early and do some mobility / dynamic type stretching. Maybe a super light cardio session if possible. Get the blood moving.
* Eat what you normally eat for breakfast.
* Last, a lot of talk of hydration. I keep a 50/50 bottle of water / pedialyte.