The pilot reported that after selecting the landing gear down he failed to obtain a safe down and locked indication. He notified the Tower of the situation, then retracted the landing gear and attempted a manual extension. He disarmed the landing gear circuit breaker, placed the selector switch to the "DOWN" position, disengaged the motor release arm and inserted the gear extension handle into the right socket, and after reducing airspeed, pushed the handle as far forward as it would go. As he was still unable to obtain a down and locked indication he landed the aircraft but the landing gear collapsed during the landing roll. Investigation determined that the landing gear functioned normally during ground testing. The navigation lights were on at the time. This automatically dims the landing gear indication such that it is difficult to see in daylight. The pilot therefore assumed that the gear had not locked in the "DOWN" position after the first extension and he elected to attempt a manual extension. However, the pilot failed to complete the manual extension procedure which requires that after positioning the handle full forward in the right socket, the handle is then inserted into the left socket and the procedure repeated. This failed to lock the landing gear in the "DOWN" position, which subsequently collapsed under the landing loads. The pilot reported that in the fifteen years he had owned the aircraft, he had never performed a practice manual extension of the landing gear in flight.