Our chool has been doing one for a long time. We take over the gym, each parent donated 2 hours of time X number of kids in the school and we have sign up sheets to fill in the needed hours, and each grade is in charge of orginizing a specific section. We collect stuff wed-Friday, Thursday is 2x the price so we as a school get first pick but we "pay for the privlage"
Friday we open to the whole school, alumi/friends and family and Saturday 9-1 we open to the public.
We arrange with got books, salvation army etc, to come and get what does not sell.
The middle school near us does one almost every year to support the science team; we all love the opportunity to pass off all the outgrown toys and pick up some new ones. But I haven't been involved in the actual operation of it, so I probably can't help you much.
I'm sure people will chime in with new information, but be sure to check the archives as there have been some good discussions on this in the past. Choose "search" while in the Message Board area and put in a good key word like "garage". You should find some useful information. Good Luck!
We just heard of a nearby school haveing a very sucessful school wide garage sale! Has anyone ever done one? We obviously know we are going to need a lot of volunteers-anything else? Any words from the wise???