If you go to Disney World in the summer, late August is best, but fall and spring are ideal times to visit, both weather-wise and for smaller crowds. December (pre-Christmas), January, and early February can be cool, but they're relatively uncrowded.
Take advantage of FastPass. This amazing (and free)convenience, now available on 24 rides, lets you get a timed ticket for the most popular rides, usually for an hour or two later. Arrive at your scheduled time, and you breeze in past the line. You can't hold more than one FastPass at a time, so it's worth checking out how long the delays are in case another ride might be available more quickly.
Check the ride boards at the parks for up-to-the-minute information on what's crowded and what's not, and head for any unexpectedly short lines. One Child reader set a 15-minute limit for standing in line with a toddler.
Go left. It sounds simple, but many people swear the majority of the herd tends to head right, both in the parks and in line.
To get a prime seat for the nightly parades and fireworks without waiting forever, schedule a meal in the right place at the right time. "We had a character dinner at the Liberty Tavern, then came outside and were well-positioned to see the nighttime parade," says one mom. Book a dinner at the lovely California Grill on the top floor of the Contemporary Resort for a fantastic fireworks view or at Narcoossee's at the Grand Floridian for the Electrical Water Pageant. At Epcot, diners at the Rose & Crown have a front-row seat for the IllumiNations show. And at Disney-MGM Studios, if you eat dinner at the 50's Prime Time Caf?, Brown Derby, Mama Melrose's, or Hollywood & Vine, you can get reserved seats at the nightly Fantasmic! show.
If you have a grandparent along who can't walk well, rent a wheelchair (available at all parks). You'll get priority seating at parades and faster boarding on most rides.