To reserve a room, you can call the Marriott Reservation Center, toll-free in the United States and Canada at 800-228-9290 or directly at 202-328-2950. To make a reservation online:   1. Go to www.marriotthotels.com/marriott/wasdt/   2. Click on Reservations   3. Click on District of Columbia   4. Click on Wardman Park Marriott   5. Select the dates   6. At the bottom of the page where it asks for group code, enter the Reservation Code for your desired room type. Room rates are available until March 26, 2002, or until exhausted, so reserve early.