I believe that you should never wait for a parking space, especially if the garage or lot is really crowded. By doing so you stop the flow of traffic, making it difficult for people to both get into and, more importantly, out of spaces. If everyone simply drives until a parked car is ready to pull out, then everyone will get a space with roughly the same amount of waiting time. By following this practice, you may increase your own personal wait-time occasionally, but your wait will also decrease at other times, as will the general frustration level of all parkers, you included.
Doesn't that make sense? Who's with me?
(Remind me to post my theory of merging when a lane ends on the highway sometime.)