CARRY YOUR RACE GEAR ON THE PLANE WITH YOU! The airline may lose your checked baggage, but at least you'll have your race clothes and shoes with you. This is the only time you want to wear your training shoes for something other than training.
NOTHING NEW ON RACE DAY! No new shoes, no new diet, no new pre-race meal, no new jog bra, no new running outfit, no new anything. Everything you do, wear or eat should have been tried and proven in training long before race day.
Respect the distance. Do the training. We all have good days and bad. The bad training sessions make the good ones that much better. When you get into the final miles of your event, your training will give you the confidence that you can successfully finish your marathon or half marathon.
WALK THE AID STATIONS. Grab a cup of water and a cup of electrolyte drink. Move to the side of the road so you don't hinder anyone behind you. Try the electrolyte drink. If it tastes like it does when it comes out of the bottle, it's too strong. Dump half of it and fill the cup with the water. If you're using energy gels, be careful about how much electrolyte drink you use. Too much of both could upset your stomach.
The purpose of walking the aid stations is to conserve your energy at the beginning and middle parts of the race. Whatever you first-timers run or walk is going to be a PR (personal record). YOU'RE NEVER GOING TO HAVE ANOTHER FIRST MARATHON so you want to make it an event you will want to remember. More good marathons have turned bad, even at the world class level, by starting too fast. Let's leave the quick first marathons to the Khalid Khannouchis and the Paula Radcliffes of the world. It's much better to be the “passer” rather than the “passee” towards the end of the race.
In most marathons you're going to experience rough spots. When this happens, just concentrate on getting from aid station to aid station. If that seems too far, go from mile marker to mile marker. Forget about how far you've come or how far you have to go. Just concentrate on the next mile marker or the next aid station. Everyone experiences these patches in a race and they will pass.
As was stated in your nutrition clinic, your diet should consist of predominantly carbohydrates. Start experimenting now to see what works for you. Eat pasta the night before your long training sessions. Try Ultra Fuel the day before your long training sessions. Try different types of high carbohydrate food before your long training sessions. You are an experiment of one. What works for you may not necessarily work for someone else.
Don't worry about getting a good night's sleep the night before your marathon. Try to get a good night's sleep two nights before your event. Most of you aren't going to get much sleep the night before, thinking about the approaching race. Get all your race gear ready before going to bed. Pin your race number on your shirt or singlet; put your gels, energy bars, candy, etc. into your fanny pack. If you eat a pre-race meal, have it ready to eat when you get up. The less you have to think about on race morning the better.
If it looks like the weather will be cold for the start of your event and you don't want to wear a long sleeve shirt, cut the ends off a pair of tube socks and pull them over your arms for long sleeves or leave the toes intact for long sleeves and make-shift gloves. When you warm up and/or the weather warms up you can discard them at an aid station. If you want to wear some inexpensive gloves you can discard, buy a pair of brown gardening gloves from Lowes or Home Depot and wash them several times to soften them up. They're also dandy for wiping your nose and not looking gross after you do so!
Cut your toenails THE WEEK BEFORE YOUR EVENT. If you cut them too short and make them sore, they will have a week to grow out.
Michael Wakabayashi's First Time Marathon Tips