I once heard an athlete aptly refer to their race day anxiety as "race brain."  The stress of race day is not just the race itself but all the logistics of getting to the starting line.  This may be exacerbated with a sleepless night in a hotel, getting up at the crack of dawn, and being off your bodily schedule.  In triathlon the swim alone is enough to put an athlete into a full blown panic attack.  Even the pros are not immune to "race brain" and I have had my own leave their nutrition at the hotel, forget their goggles, and not pump up their tires; rookie mistakes!  Although you can't completely rid yourself of race day anxiety there is a lot you can do to lighten your mental load.  These five tips are a good place to start!

1. Have everything ready to go the night before the race.  Seems elementary but so many race day meltdowns are caused by equipment malfunctions or forgetting an essential piece of equipment.  Have a list, check it twice, and leave nothing for race morning when you will have enough on your mind.  Leave race morning for a few steps such as prepping your bike, getting your wetsuit on, or warming up your run.  Know where everything is and put it in the right place; even practice getting set up.  Race day should be a well rehearsed process, not a frantic last minute preparation.
2. Know the lay of the land.  With so many things on your mind getting checked in and ready to race can cause a lot of anxiety.  You can greatly reduce this by knowing what to do and where to go.  Race directors know this as well and often allow check in the night before; which you should take advantage of.  The more you can take off your place the better.  Know where to park, check in, and where the start is.  Each race may have a different process so read the pre-race instructions carefully.  Feedback from athletes that have raced the course can be invaluable.
3. Race day is not a day to test new equipment.  Although it may be tempting to try a new pair of shoes, helmet, computer, or energy bar- DON'T.  I have witnessed so many calamities that could have been easily avoided by simply racing with what you know.  These include blistered feet, upset stomachs (or worse), leaky googles, computers that drive the athlete batty, and a new bike fit that causes more pain than it was worth.  If you purchase something at the expo leave it for the next race when you have had a chance to vet it out.
4. Those butterflies should be telling you something.  When nervous our digestive systems function differently.  This may cause race morning GI issues that only increase anxiety and affect performance.  Do not eat the hotel buffet on race morning and certainly do not eat something you are not used to.  If you are not acclimated to training in the am you may want to stick with a breakfast that is lighter and easily digestible as your system is not used to be stressed in such a way at 7am.  Try to eat well before the gun goes off and stick with easily digestible snacks to keep your blood sugar up, tapering to the start of the race.  Avoid a lot of protein and fat, in short give your GI track some latitude. 
5. Train your body to be calm.  You have trained your body to expend your energy but you have likely not trained it to be calm and focused at the starting line.  A simple technique is to take slow deep breaths over several seconds and exhale slowly.  While you do this visual something positive or repeat a mantra.  One of my athlete's mantras was "calm, rested, ready."  Slowing your breathing actually tricks your body into relaxing.

One of the best ways to limit race day stress is to of course be well trained for the race, but these simple steps will greatly reduce your chances of a race day calamity.  The less you leave to chance and the better.