Ok, I'm just going to spill it. Let's assume, I have a competition on sat, static startup at 13:00 (this applies to only static). So this is my competition routine as it currently stands (it always keeps evolving of course)
First, 2 weeks before the competition, I stop all cardio, gym etc. I also change my diet slightly to lighter meals. If I loose a pound or two in the coming weeks, I'm confident. But you should not be starving. Just eat normal...I also start regular dry/wet statics, pertty much every day.
On comp. week training would be:
mon static, tue, static, wed rest, thu rest, fri static. I sometimes do 2 days of static before a comp, but usually only one. I don't know the scientific details of it, but the best statics for me are always done at the end of a 2-3 day succession of max static daily.
Days ahead, I make sure I have a coach and go through with him what I need. After my warmup starts, I don't want to be worrying about anything else than holding my breath. Start times, choosing lanes, arguing with judges...That's all for the coach.
On starting from friday evening, I will eat no solid food. I make sure I drink enough (but not too much). I try to get some good sleep, but usually am too nervous and have problems falling a sleep.
On saturday I will continue with the non-eating, but drink a few "nutridrink" meal replacement thingys every few hours, the last one 2-3 hours before start. I make sure I drink enough water (but not too much!) and may pop a few electrolyte supplements if I'm feeling nervous about over-hydration.
45 minutes before start, I sit by the pool with my clothes on and amuse my self by marveling at the n00bs rushing into the water too early

I then change into my wetsuit.
About 30 min before start I slip into the water and start my warmup. I'll post here my warmup times for reference, but it's pointless to copy it. But it's something you can start working from if you have no other ideas. Of course you have to "convert" the times to what ever you target is. Let's assume a target of 7:30
-First I do an easy FRC static just to sort of settle down and get to feel the water
-Relax for a minute or two
-FRC Static 3-4 minutes
-Relax for a couple of minutes, breathup about 5 deepish, slow breaths
-FRC Static 4:30
-Relax for a while, wait for previous competitors countdown to official TOP, maybe do a pack stretch
-Start with the countdown of the previous diver, full inhale static, 6 - 6:30 minutes
-At this point I should have about 5 minutes on the clock. I just close my eyes and relax
-When the annoucer says 2 minutes, I put on my nose clip
-At -1:30 I start to slightly deepen and control my breathing
-From 1:00 I do 4-5 deepish breath cycles
-At -0:30 I start packing
-At 0:05, still packing...
-0:05 packing, packing, packing...
-Roll over and start
Then I just sort of try to empty my mind. But if it's a competition, various things will be running through my head for the first minutes, but the first signal at 4:00 usually comes as a pleasant surprise if everything has gone right
At 4:30 - 4:45 I get the first contraction. If it's over that, I worry...
Then I just count the contractions to pass the time and make my way to the minimum target. Usually I set it at 6:30. This is the "no bailout" target. It has to be ambitious enought to require an effort, but low enough that I really don't need to bail out. If I'm still feeling good, I keep going. I don't do any weird tests to check my conciousness. I know when I've had enough intuitively somehow.
About 20 seconds before I get up, I put my hands on the edge of the pool and bring my body upright. This has 2 functions. First, it feels good and I can steal a couple of more seconds, second I get ready to get up with minimal movement and good support. Don't want to dip into the water and mess up the SP just because I have bad support from the ledge, plus it's a safety thing. Even with a severe samba, I have a better chance to stay above water without help.
Right before I get up, I blow out some air. This is so I can steal even the seconds I would be exhaling after getting up to my performance and when I get up, the first thing I can do is inhale.
I lift my head up enough to breathe, but not all the way up. I take exactly 5 deep breaths before doing anything else. Just supporting my self, face down, breathe, breathe, breathe...I have timed it and 5 breaths is what I can do while still having a healthy few seconds to complete the SP. I also do this in every training max static so it becomes second nature instead of a concious process. Therefore I do it the same way even when close to the limit.
I then remove the noseclip, stare the judge in the eyes, show the ok and say "I'm ok". This is also done in every training max static.
So there you have it. Things that people will not agree with or may want to add/try:
-Last warmup, I don't know many that do an almost max performance just before top. But it works for me
-You may want to settle down for a couple of hours before start. Go somewhere peace full and relax.
-Some light stretching may help
Then there is the no warmup/no breathup school. I agree that if you have the will power, the less breathup you do, the better. All it does is make the breathing reflex easier to tolerate. I have gone down from bordering on hyperventilation to 10 deep inhales and finally now down to 5. About the no warmup I'm not so convinced, but some swear by it. I can do about 90-95% performance with that method, but the consistency is not very good. If you want to get that to work, you need to train it a LOT.