In addition to many excellent comments already:
Show up a full day or two before the opener, stealthy scout the area, locate exactly where you're going to be first light on opening morning. Keep all noise and movement to a minimum.
Don't camp in creek bottoms, the cold air settles in the bottoms and the sun doesn't reach there often. Don't camp on ridge lines even though they may be flat and sunny - the wind will get you most times. Keep your camp clean and food stuffs hung away from camp, bears do show up during the dark of night. Eat fatty foods before bed time on cold nights. Spend extra time to COMPLETELY clear your bed area. Drink water even when you don't seem thirsty and eat lots of calories.
If you're freezing your ass off, get up and work up the fire. Shivering the night away doesn't do you any good.
