The biggest mistake people make is “they have no idea of pacing,” says Greg McMillan, founder and head coach of McMillanRunning.com. To avoid making that mistake, McMillan recommends doing a few short workouts at goal pace about two weeks before. For a 5K race, that might mean doing 6 x 30 seconds at 5K pace or, for a half-marathon, running 6 x 800m at half-marathon pace—not faster.
Jay Johnson, author of Simple Marathon Training, agrees. Pace is an important thing to nail down in the final weeks, including at least one race-pace workout in this period. For example, he says, if you’re getting ready to run a 5K, then maybe do 10 x 400m, with a five-minute jog, then a hard 800m.