COMPLETING AN IRONMAN, with its 2.4-mile swim, 112-mile bike, and 26.2-mile run, is definitely doable for any fit athlete. But completing the Ironman, in Kona, Hawaii—the gold standard of endurance events and the official Ironman Triathlon World Championship—is truly worth the effort to get there. On race day, you'll swim the 80-degree crystal-clear waters of Kailua Bay, cycle through Kona's legendary lava fields, and get a final emotional push while running down Alii Drive during the last half-mile as the huge crowds cheer you on. There are almost no rank beginners at Kona—only 150 spots are available by lottery for U.S. citizens, and the rest of the American field must qualify by finishing a half Ironman or longer race. But getting across the finish, no matter what your time—I placed 159th in my first one—is a milestone you'll never forget.

Go for It

Take your bike, running shoes, and swimsuit to camps run by Multisports.com. The three-day clinics, conducted at each of Ironman's five racing sites in the lower 48, will have you swim, bike, and run the entire course, then glean training and racing tips from Ironman Triathlon pros Paula Newby-Fraser, Paul Huddle, and Roch Frey. $695; 760-635-1795, www.multisports.com

SKILLS & TIPS: Practice "T2," the bike-to-run transition, which will hit you hard after a 112-mile ride. Do it at least once a week; even if it's just a short run after a bike ride, you're conditioning your legs to get used to running after biking. Train solo sometimes, as it prepares you for the solitude of the race. Ride challenging routes on windy days, because race day is always windier than you expect. When racing, don't push too hard on the bike—that happens even at the pro level—as it leaves some serious carnage on the road by the end of the marathon. Similarly, hold back for most of the run; if you feel good with 10K to go, then pick it up. Don't speed through the transitions: If you forget a hat or sunglasses, or leave with a rock in your shoe, it could ruin your race. Finally, eat often. Even a 100-calorie deficit can affect your performance.

TRAINING: Before you tackle any Ironman, you should have worked your way up through three half Ironmans in a year and be able to easily ride 100 miles and run for two hours straight in the same day. Four months out from the race, set up a weekly training plan, with 20 percent of your time spent swimming, 30 percent running, and 50 percent on the bike. The bike is the best place to build endurance—it doesn't beat up your body, like running does, but the muscles you strengthen while cycling also help with running. Your biggest training week is five weeks before the race, when, at a minimum, you should spend nine hours on the bike, 5.5 hours running, and 3.5 hours swimming. Then taper your workload by 25 percent each of the following weeks. During the final week, do very little, as an injury or overexertion at this point can hurt your race. Arrive five days before the event, to adjust to climate and time changes.
—As told to Dimity McDowell