"You have no idea what's going to happen and how you're going to feel and where you going to hit a wall," said Santa Monica resident Tanna Frederick, an actress.
Frederick took up running to work through career stress. She plans to make this year's L.A. marathon her fourth.
"It's all about accomplishing something for yourself," said Frederick.
Whether it's a full 26.2 miles or a half at 13, you have to have a plan.
"The biggest thing to prevent injuries and to get as much enjoyment out of the experience as possible is to not rush the experience," said Jason Karp, author "Running a Marathon for Dummies."
Karp says too much too soon is the cause of shin splints and other injuries that might end your plans.
"If you're already running about 8 to 10 miles right now, you do have some time to get ready for the L.A. Marathon," said Andrew Kastor, coaching director, Los Angeles Marathon.
Kastor says there are ample running opportunities to do another if you aren't ready for the March race.
"For a beginning athlete I recommend three to four days of running, maybe with one or two days of cross-training," said Kastor.
Yet his elite runners now run 15 times a week.
"Increasing your weekly mileage by between 5 and 10 percent will help minimize the risk of injuries," said Kastor.
And of course everyone knows that warming up before your run is very important, but Kastor says that it is important to stretch before you warm up.
"I'm a big fan of active isolative stretching," said Kastor. "You can roll out of bed and start doing these stretches because there is a nervous system component that helps protect the muscles."
Work on stretching to loosen up lower back and thighs, chins, ankle stability, calves and tight hamstrings.
Then there's fuel. Both coaches choose kid-friendly foods.
"Chocolate milk is actually a fantastic post-workout drink, because it's high in carbohydrates, high in protein," said Karp.
"The best post-run breakfast is French toast with some eggs," said Kastor.
And start testing now, so whatever you plan to eat the night before the race, as well as the morning of the race, sits well.
Both coaches say you should have a few pairs of shoes that you change out throughout the week. Replace the shoes after 400 to 500 miles.
"Running a Marathon For Dummies" is Dr. Karp's fifth book. It is available in bookstores nationwide and at Wiley.com and Amazon.com.
Elite Asics Coach Andrew Kastor is now the official running coach for the L.A. Marathon: www.coachkastor.com
For more information about this year's Los Angeles Marathon: lamarathon.com