This advice is Assuming this is a woods race. If its not ignore me lol.

Hydrate. Start today. You cant be too hydrated.

Dont worry about getting a great start, or winning. Its your first race so use it as a learning experience. As long as you finish i can pretty much guarantee you wont get last.

If there is a tricky obstacle slow down a bit to pick a good line and make sure you get good drive to get through it. Falling over on a hill or something zaps energy like crazy. And wastes time.

Wear a camelbak

Bark busters

When the leaders come around get out of the way quickly, but don't crash trying to do so. The last thing they want is someone crashing in front of them.

Have fun