How early you get up before a race depends on personal preference. Allow yourself enough time to go to the bathroom--Hell, I like to go twice before racing--eat if you need to, and get dressed and to the race with plenty of time to warm up.
Practice your pre-race routine during your training. Not all athletes’ bodies respond to the physical and emotional stress of racing the same way. Some people require food in their stomach the day of the race, while others must race with the tank on empty. If you eat, usually a bland form of complex carbohydrate works best. When I raced, I ate a bagel--a New York bagel, of course--and a banana. This combination worked well for me. Both items were relatively easy to digest and seemed to settle my stomach. An added benefit was the banana’s potassium, which helped prevent muscle cramps.
Finally, getting plenty of pre-race rest and sleep works to your advantage. Try to get a good night’s sleep two consecutive nights before the race. More likely than not, the night before the race will not be the best night’s sleep of your life. Bank a few extra hours the day before.
When arriving at the race, take care of business before socializing. If there is a check in, get that out of the way first. Next, while warming up, discover where the aid station(s) are located. Finally, your last to-do involves determining who is in your age group. If your goal is an age-group medal, then knowing something about your competition certainly helps.