You would think that guys with the athletic ability to run sub-five-minute-per-mile pace in the marathon would never screw up during a race. But the truth is, even for the pros it is all too easy to blunder during a 26.2-mile slugfest of aerobic pain and pounding. And on Monday, when dozens of elite runners pass the finish line of the 118th Boston Marathon, many of them will have made some sort of mistake before the race or along the way. Here, the top three U.S. contenders among the men in this year’s Boston—U.S. half-marathon record holder, Ryan Hall, 2012 Olympic Trials winner, Meb Keflezighi, and 2012 U.S. half-marathon champ, Abdi Abdirahman—share their (hard-earned) knowledge of what no runner should do before or during a marathon.

1. Don’t blow your regimen right before the race.

The week before a marathon is not the time to log one last super-hard long run. “A huge mistake I see runners making is trying to prove to themselves that they are fit in the last two weeks,” says Hall, whose 2:04:53 at Boston in 2011 is the fastest time ever run by an American. “A week before the marathon, I’m doing my easiest 90-minute long run of my training, not pounding out 20 hard miles to prove to myself I’m fit.” Hall says it takes extraordinary confidence to trust your taper. “A couple of years back, I ran a 15-mile hard run 10 days prior to the New York City Marathon,” says the Flagstaff, Ariz.-based runner. “As a result, I was super flat on race day, despite the fact I was in the best shape of my life.”

2. Don’t worry about sleeping the night before—worry about sleeping two nights before.

Most runners don’t sleep well the night before the marathon. But let it stress you out, and you’ll hurt your performance more than if you stayed up all night playing video games. “Two nights before the race is the most important night to sleep, not the night before, especially if it’s a morning race,” says Keflezighi, adding that he’s happy if he gets two to four hours of sleep before a marathon. Still, it’s important to rest and stay off your feet the night before. “Just stay in your bed with your eyes closed, and don’t wander around. That way, you’re still resting,” he says.

Meb Keflezighi, Ryan Hall and Abdi Abdirahman compete in the U.S. Marathon Olympic Trials in January 2012 in Houston, Texas. Getty Images

​3. Don’t change your diet.

Just because the fastest guy you know eats some strange pasta the night before a race doesn’t mean you should follow his lead. “Some people try to eat differently, but you should just eat your routine things,” says Abdirahman, who trains in Tucson. “Most runners eat well throughout the year, so just do what you normally do—that’s the safest way.” Also think twice about taking dietary supplements and over-the-counter drugs like ibuprofen, even if you’ve used them in training. “Even though I hadn't previously had a problem with ibuprofen affecting my stomach in training, I had a big problem with it at the [2012 Olympic Trials],” says Hall, who took Advil before the race for a sore foot. “My stomach started feeling pretty nauseated about halfway through, and I started feeling like I was floating out of my body by mile 23.” Hall still finished second, making the Olympic team, but only by running the “longest three miles in my life,” he says.

4. Don’t spend too much time at the pre-race expo.

Every marathon has a big, flashy expo so that companies can try to sell a bunch of new stuff to amped-up runners. But as tempting as it is to tour this maze of goodies and giveaways, Keflezighi says don’t do it. “People get excited and walk around there for three to four hours the days before a race, and that’s just so bad for you,” the three-time Olympian says. “I can do expos before a half-marathon, but my sponsors understand I can’t be on my feet before a longer race.”

5. Don’t wear new shoes.

At some point, every veteran runner messes up by wearing brand-new shoes the day of a race. It happened to Abdirahman several years ago when he picked out a new pair before a road race and ended up crippled and bloody with blisters. “You just never know how they’re going to work,” he says. Keflezighi says that runners often get talked into buying new shoes at the expo and then wear them race day. “That’s just asking for blisters and other issues,” says the San Diego-based runner. And remember: A new version of the same model you’re used to training in can still cause problems due to slight differences in stitching or overlays.

6. Don’t turn into a head case on race day.

It happens to every elite runner—that awful time before a high-pressure race when you let every negative thought about your fitness and performance creep into your thoughts. “[Legendary coach and U.S. marathoner] Alberto Salazar expressed it best when he said, ‘We are all wimps on the starting line,’” Hall says. “No matter how well my training has gone or how confident I’ve been for months leading up to a major race, I always find myself battling negative thoughts like, ‘I’m not feeling good, so I’m not going to race well.’” Hall says the best way to fight negative thoughts is to accept them as part of the process and then move on. “Instead of believing I’m not feeling good, therefore I won’t run well, I acknowledge that, yes, I may not be feeling that good, but the truth is I rarely feel good on race week and I usually run well, anyway. The key is to acknowledge the truth in the lie, and then change the lie into something positive,” he says.

Meb Keflezighi is greeted by New York Road Runners President Mary Wittenberg after he crossing the finish line in the New York City Marathon in November 2013. AFP/Getty Images

​7. Don’t wear a watch.

You might see lots of runners at the starting line ready to start their watches the moment the gun goes off, but that doesn’t mean it’s always a good idea to wear one. Abdirahman says he never wears a watch during the marathon because, “I don’t want to know how fast I’m going—I want to just go,” he says. The four-time Olympian says ditching your wristwatch also forces you to run your own race—not the race you think you should be running. “It lets you run how you feel, how your body feels,” he says.

8. Don’t forget to lube.

A little lube—or, better, a lot of lube—can save miles of pain and chafing during the race. “You have to do your private parts, your nipples, your feet, under your arms,” says Keflezighi, who lubes up every week before his long run. Even though it’s normal practice for the 2:09:08 marathon doesn’t mean he hasn’t messed up in the past. “This last year at New York City, I ended the race with a big cut almost two-inches long across my lats,” says Keflezighi. “I put Vaseline on beforehand in my hotel room, but I was in a rush and didn’t put on enough. So it’s always better you over do it then underdo it.”

9. Don’t overdo your warm-up.

Don’t run a race before your race starts. “You don’t need that much warm up—just a half mile or mile to get the blood going,” Abdirahman says. That’s much shorter than most hardcore amateurs are used to doing before a 5K or 10K, but Abdirahman says marathoners need to conserve strength for the longer distance. That’s why he’ll just run a mile and stretch before Boston, he says. “You can warm up while you’re running the race.”

10. Don’t run with someone else.

Lots of amateurs and some pros will try to keep up with a friend or training partner during a race, but doing so is a good path to a DNF. “You have to run your own pace, what feels comfortable for you,” Abdirahman says. The four-time U.S. 10,000-meter champion, with a personal record of 27:16 at the distance, says that he has made the same mistake several times throughout his career. “In 2007, I was in the Netherlands for a 10K, and I thought I was ready to run low-27s [minutes overall],” he says. “So I went out the first 5K at 13:15 [14 seconds slower than the American men’s record], and I paid the price.”

More From Sarah Toland:

Chef's Table: Cooking for Sports' Superstars

Playoff Preview: NBA Star Trainer Tim Grover On What It Takes To Win​

Coaching the Masters: 10 Tips for Mastering the Moment​

11. Don’t forget to drink.

“The biggest mistake people make is waiting until they’re thirsty to drink,” says Abdirahman, noting he’ll sip water or sports drink at every 5K in Boston. Keflezighi also prioritizes drinking during the race, but says a runner’s hydration should start four to five days before the marathon. “If you drink a lot of water only the day before the race, you’ll wash out all your nutrition and electrolytes,” he says. “You need to start early and have to go to the bathroom frequently the days before the race—but not so much that your urine is always clear.”

12. Don’t race the first five miles—race the last 10K.

“The way you should treat a marathon is like 20 miles of running, and then 10K of racing,” Abdirahman says. “Especially in Boston, you need to save your energy for the last part of the race.” Every elite runner worth his or her salt knows the best approach to racing a marathon is to negative-split it, meaning you run the last half faster than you do the first. “People usually get impatient,” Keflezighi says. “They just want to go harder and harder. Some people do crazy surges at mile 6, mile 8, mile 10—but you still have 16 miles to go. So you have to modify your pace and adjust.”