Great question.
Any socializing and drinking the night before is moderate. My routine begins with getting clothes, equipment and bag prepped for anything that could conceivably happen. After everything's ready I relax, put my feet up and mentally play the course(s), concentrating on clear targets and clean lines. I play each hole, first with pure throws, then again in bad throw/bad break scenarios, scrambling to save strokes.
I've become a Bob Rotella disciple over the last couple of years, and when time for bed I fall asleep reading one of Dr. Bob's books. Lately it's been
The Golfer's Mind, which I've read a dozen or more times.
After waking I get the morning routine out of the way and eat a solid breakfast, easy on the fats, sweets and meats (yeah, I know, what's left?).
Arriving at the course I religiously stretch, then warm up my senior-GM arm throwing tennis balls FH and BH against a wall about 50-60 times (equivalent to a 30-minute field warmup chasing discs). Afterwards, I move on to practice putting and throwing a few of the holes.
The most important part of my pre-start routine comes prior to walking to my first hole. I go off by myself, close my eyes and tell myself there are four thoughts - and only four thoughts - I will have on every shot:
> Think only of what I want to happen.
> Focus solely on my target.
> Trust my throw.
> Accept the result.
If I do this well, and embrace the process rather than the result, I play relaxed, committed and without doubt. I firmly believe, and have witnessed, that the better I can control my thinking, the better I play.