Nutritionally, it is important to make sure you fuel adequately for the time you will be running, not for the distance. Trail races can be significantly slower than road races. If possible, run the course before you race it. If you don’t have an opportunity to run it, look on-line for any course elevation profiles, photos, or descriptions that are available. Also look at race times from previous years to determine a realistic pace that you can expect to run. Race duration will determine whether a pre-race meal is sufficient to meet your energy needs, or if you need to bring something along for mid-race refueling. Refer to Debbie Perry’s article on pre-race nutrition for more details.
As for equipment, it’s important to be prepared for a variety of conditions. Just like any outdoor race, you should bring layered, synthetic clothing for hot or cold, wet or dry weather. Unlike the road or track, however, you also need to prepare for highly variable terrain. Trail conditions can deteriorate overnight with a sudden storm. Bring shoes for any scenario you can reasonably anticipate. Here in the Mountain West, trail racers or trail trainers are usually sufficient. But if you prefer a lighter, more flexible shoe, there’s nothing wrong with using a road trainer or even a road racing flat on the trails (ideally one with decent traction in the outsole). If you’re on grassy, soft trails like those typically found in the East or Pacific Northwest, it may even be appropriate to wear a cross country or track spike.