Of course you will have followed some sort of training regimen, and should be confident with the miles you've pounded into the pavement in preparation for the big day. This is important not only for your body, but also to get your mind strong enough to push you through the difficult later miles. You might have even done strength training to get your body ready, and that's great! Both of those will prove helpful.
But you can't forget the checklist: the valuable list of tasks to complete before, or items to bring with you on, event weekend.
Logistics are crucial. Make sure your hotel is booked and confirmed well before race weekend. Keep an eye on the weather a week before. Know how you are getting to the event on the morning of the race. Are you driving yourself? With a friend? Being dropped off?
Know packet pick-up location, times and rules. Will there be parking costs and where are parking lots located (this is good to know both for packet pick-up and for race day)?
Study the race route. Write bathroom, water and food stops in permanent marker on your arm the night before, on your water bottle, or on a laminated scrap of paper you can carry with you in your running gear.
Make sure your cheering section is prepared with items they will need, like race routes with your estimated arrival times for every spectator spot, road maps or GPS, any signs or cowbells they will be displaying, and snacks and distractions for the younger spectators. Make sure your cheering section also knows what you will need from them during the race, like energy gel packets or water refills at certain mile markers. Make a plan of where you will meet at the finish line.
Plan your meals for at least three days before the race. Research good foods for pre-race preparation and listen to your body. Avoid too many sugars, fiber and anything else that has the potential to increase your chances of gastrointestinal issues during the race.
Drink a lot of water every single day for the entire week before the event. A good daily intake rule is for every pound you weigh, drink an ounce of water- so if you weigh 142 pounds, try to drink 142 ounces of pure water daily. Don't worry about planning for food or beverages after the race, there will be a ton of free food and drink for you to devour at the finish line.
Make sure the running clothes, socks and shoes you plan to wear on race day have been worn before. This is the absolute worst time to wear brand new running clothes, even if they are adorable. Run in what you know works for you. The last thing you need is chafing nipples and thighs, or new blisters at mile 5 of your event.
Know what you will be carrying with you while you run. Water? Energy gels? Baby wipes? Kleenexes? Vaseline? Headphones or arm band? Phone? Headband or hat? RoadID tag? KT tape? How will you carry these things? If you can, do a long practice run carrying and/or using these items.
Buy a new audiobook, update your playlist, or get your podcasts downloaded the night before the event. Race morning will be busy enough- you don't want to worry about getting your music ready just before the the gun goes off.
Lay out everything you will need the night before, from what you will eat for breakfast, to every item of clothing you will be wearing. You will be anxious, excited and nervous the morning of the event and being prepared will help calm your adrenaline rush.
This list covers most of everything you will need to remember, but be sure to tailor it to your own specific needs. There is much to consider when preparing for the race, but you want the big day to go perfectly. You have literally run hundreds and hundreds of miles during training to get to the point of being able to prepare your body and mind to run a half or full marathon and you don't want a little forgotten detail to get in the way of your success.