Plan as far in advance as possible--not just weeks, but months ahead. You'll end up with your first choice of accommodations, plane reservations and everything else.
Go beyond just reserving your lodgings to making reservations at restaurants, and purchase tickets at events/performances you want to attend. Sometimes it can be fun to leave your schedule open, but if you do so on a busy holiday weekend you might end up eating at diners and watching the clouds go by for entertainment.
Call ahead to confirm your reservations before leaving. Getting stuck at the airport without a flight, or at the Jersey Shore with no place to stay, can be a real disaster on a busy weekend.
Do whatever you can to avoid the peak travel days/times to be in transit. Driving out of Los Angeles, for example, at 4 p.m. on the Friday leading into Memorial Day is just begging to sit in traffic for three hours.
When flying, be sure to get to the airport about three hours before your flight leaves. The worst thing that can happen is ending up sitting at your gate for an hour or so, waiting for your plane. Still, that beats the stress of cutting it close and possibly missing your flight.
Consider exploring less-traveled, more remote sites on such a weekend. A destination like Martha's Vineyard or Yellowstone Park on the Fourth of July weekend is going to be totally overrun with tourists.
