Don't try anything new on race day
Stick with your usual schedule and routine. Wear the same clothes and shoes that you usually do, eat the same food, and drink the same stuff. Throwing in an "unknown" can send your day spiraling off into unknown space or at least make you really, really uncomfortable.
Take weather in account
Check the weather when you get up and dress accordingly. If it's going to be warm, dress light, bring water, and be ready to run slower. If it's going to be cold, dress in layers, bring the chapstick, and be ready to remove layers as you get through the race.
Bring someone along to cheer you on
Ask a friend (or a few friends) to come to the race and urge you on from the sidelines. You won't believe the power of hearing a familiar voice screaming your name and cheering you on, especially when you hit that last mile or two and not sure if you're going to make it.
You might also want to write your name on your shorts or bib so others – volunteers, spectators, and other racers – can urge you on by name. Make sure to do the same for others around you!
Arrive at the race site early
Race days are usually crazy with people running around, participants trying to find their space, people milling around watching the chaos, and race coordinators trying to keep it all under control. No matter how efficient you are or how many times you've been to the site before the race, it's going to take you a lot longer than you think to find parking, check-in, and find your spot. Arriving early will allow you to do all of that and enjoy the race atmosphere without feeling like you're in a rush.
Attach your race number and / or computer chip
Attached your number to your shirt as the race officials tell you to. You'll need at least four safety pins to ensure that your number stays on without flapping around and annoying you. (Yes, you'd be surprised at how annoying an ill-placed race number bib can get by mile 10.)
Also, make sure your computer chip is securely attached to you. This little chip is usually attached to your shoe string, clothes, arm, or wrist and will help race officials to track your progress. Check with the race officials to find out the best way to attach it.
Warm-up Before the Race
The last thing you will want to do is to start a long race with cold muscles. Without stretching, you have a higher chance of injuring yourself in the first few miles of the marathon. Your best bet is to start stretching about 30 minutes before the race begins.
Take Your Time
When the race begins, take your time. Run more slowly and walk a little more at the beginning of the race to help your muscles get into the groove of running. You have 26 miles to go – take your time and let your body get acclimated to the task in front of it.
As the race progresses, keep to the walk-run ratio that you are used to. When it comes to your first marathon, it's more important that you finish the race rather than come in first. The more energy you conserve at the beginning of the course, the stronger you will finish at the end.
Almost all runners know that it's super important to stay hydrated while they're running, but it's even more important in a distance running event like a marathon. To stay properly hydrated, experts say that you should drink at least 8 oz. of water or sports drink every 15-20 minutes. Bring your own bottle for the first few miles and then take advantage of the refreshment stands along the way – that's what they're there for!
Don't Stop At the Finish Line!
When you hit the finish line, you're going to want to immediately fall over on the grass and die. DON'T! That's the worst thing you can do for your body after a long, stressful run. Your best bet is to walk for at least 30 minutes. This will allow your muscles and heart to cool down and get ready to rest. You might want to mix in a few good stretches into your cool down to help the rest of your body to relax and stretch out.
Make sure to eat and hydrate after the race
It's important for you to replenish all of the nutrients and water that you lost in that long run. Drink water or sports drink as you walk and have a snack when you're done, if you stomach can tolerate it.