Line Up With A Pet (Please Don't)
You may enjoy running with your dog, or while pushing your tot, but other competitors probably won't. It's tough enough navigating around other runners, let alone dogs and strollers. You also can't be certain how your pet or child will handle the race scene, says Curl.
What's more, the medical teams may not be equipped to handle pets or children who get sick or injured. That's why many races ban both. It's smarter to seek out fun runs that promote a casual atmosphere, he says.
More: 3 Tips for Running With Your Dog
Wear Headphones (Maybe Not)
Portable listening devices are allowed in most races as long you're not going after medals, awards or prizes, and you're not using it to take calls from your coach. That said, even if your race allows portable tunes, it's best to turn them off before the start.
"Folks who wear headphones might as well be on another planet," says Helbig. "They don't hear anything, whether it's a car or you yelling at them that they need to turn here."
If you must run to music, use just one earbud and keep the volume low: You need to be aware of what's going on around you.
Run With A Partner (Maybe Not)
Racing with a friend can help you maintain your pace and provide encouragement. But if you're running side by side, you could be blocking the path.
"Work together to be conscious of people around you," says Brookman. "And never run more than two abreast."
Agree on a signal to go from two wide to one, and decide who'll go first every time.
More: 5 Race-Day Mistakes to Avoid
Lunge for Water (Please Don't)
"There's plenty of water and sports drink," says L.A. Marathon's Curl. "We're not going to run out."
So instead of diving for the first cup you see, skip the first tables, which are likely to be the most crowded, and set your sights on the end tables. From a few yards out, make eye contact with a volunteer and point to the cup. Then, after you take your drink, exit gracefully.
"Look before you turn back into traffic," says Curl.
If you're taking sports drink, be sure to toss your empty cup into a trash can or to the side of the course. Would you want to run the rest of the race with a sticky leg? The person behind you doesn't either.
(Related: Avoid these 5 Common Pre-Race Nutrition Mistakes to make sure you stay fueled and hydrated.)
More: Half-Marathoner's Guide to the Aid Station
Chit-Chat (Please Don't)
No one expects you to stay quiet for an entire race. But skip controversial topics. And don't ramble.
"Pointless conversations show a lack of respect for the other runners," says Bart Yasso, this magazine's chief running officer. No social media, either: "You're not really racing if you're Tweeting or texting."
Spit or Blow (Go For It!)
Sometimes you have to do it. But try not to hit anyone else—and that goes for, well, all bodily functions.
"Spitting, power snotting and passing gas are going to occur while running," says Rob McCrone, head running coach at The Energy Club in Arlington, Virginia. "Just make sure there is no one behind you when you do it."
Performing a quick 360-degree survey of those around you before you let loose will give you peace of mind. And if you know you frequently need to spit or blow your nose while you run, hug the curb (or learn how to do it right—watch 5 Steps to the Perfect Snot Rocket)
More: 10 Running Rules to Remember