Kailua Beach
Where windsurfing really came into its own - home of Robby Naish, etc.
Excellent spot for beginners and intermediates. Protected by reef, the waves at the beach are small. Easy entry from sandy beach. Adequate rigging area with nearby parking. (parking very crowded on weekends though!).
Trade winds are side/on-shore. Usually moderate, although occaisionally stronger. (Go to Maui for consistently strong wind.) Some wave sailing available along reef or further down the beach, although Kailua is better suited for slalom/freeride/freestyle.
Several places to rent gear are nearby, although not in the beach park itself. Two or three trucks with rental gear are usually there Monday-Friday and Saturday until noon.
Windsurfers and kiteboarders are expected to rig back from the beach so as not to interfere with other users. Rigging and entry areas are at each end of the beach park. Do not use the middle area - this is a guarded swimming area.
Kiteboarders and windsurfers generally get along well here -- keep it that way!! Kiters generally launch/recover somewhat more downwind than the windsurfers, although that is a matter of courtesy rather than some formal rule. (Courtesy goes a long way - use it.)