Actress Vishka Asayesh in the Swiss marathon

One of the most common causes of injury is building weekly mileage too soon, too fast—so don't underestimate the importance of consistently running at least 20–30 miles a week regularly before committing to training for a marathon.

Start small: Running a few shorter races—5Ks, 10Ks, or even a half marathon—is an excellent way to prepare physically and mentally for a first marathon.