Do not over taper
Most age-group marathoners tend to over taper. As a standard rule, decrease your mileage by 25 percent two weeks out, and another 25 percent on the final week. Include a run (two to four miles) at marathon pace early in the week before the race, simply to avoid feeling stale.
Stick with what you know on race weekend. If you normally eat rice and beans the night before your long runs, stick with it. No new foods, and no new clothing or shoes.
Have a plan for your race and execute it
Go over your plan in your head and do not veer from that plan. If you are trying to run 9:20 pace, do not push the pace in the first 10 to 15 miles. Dropping into the sub 9:00s will bite you after 30K—no matter how well you feel.
Negative split your race
Unless you are running a course with a downhill start, the best way to set yourself up for success in a marathon is to run the second half of the race faster than the first. More than 85 percent of the fastest marathon splits have been run this way.
Many new runners should avoid the marathon for two to three years in order to gain experience in shorter distance events. Runners set on completing a marathon should do so with the aforementioned tips in mind.