Most resort-town lodgings are booked far in advance in summer, but occasional cancellations mean you can sometimes travel on a whim. In beach areas, many lodging properties offer their guests day-use beach passes, giving you access to sandy stretches reserved for residents. Some places on Fire Island and on the North and South forks institute three-night minimums during the peak season. Island real-estate agents have listings for seasonal and weekly rentals, and local chambers of commerce can point you in the right direction for a place to stay.