How do you handle a meltdown?

How do you handle a meltdown with your aspie or autistic child?  I know for my wife and me it is still very hard, however over time we have been able to limit them.  Meltdowns are quite common and usually occur because of a change in schedule or procedure or noisy crowds.  The hardest thing about meltdowns in public is people often look at you as if "you need to control your child" but most people don't understand what that child is going through.  A couple years back at a Target store when David was going through a meltdown there was a man, probably in his 40's, that seen the incident and mumbled under his breath to his children "what that kid needs is a good ass whoopin'" and naturally that comment didn't sit right with me so I turned around and asked the man "so you think I should show my child that violence is okay when things don't go right?" and left it at that.  These days we usually stick to a schedule and before going out we inform David of everything that we are going to do so he is not surprised when it happens and so he can prepare for crowds.  This so far has been the most effective way of curbing the meltdowns, however it does not completely stop them.  Another subject that usually causes meltdowns is when people, usually little brother Jack, play or touch his items.  He is fine with most items but it is the prized possessions that he doesn't anyone to touch or sometimes even see because of the fear that they may break or ruin it.  Usually to prevent this we tell him to put all of his prized possessions (potbellies, Harry Potter books, Shel Silverstein books, signed baseballs and others) out of the reach of his little brother and to make sure that if he doesn't want anyone else to touch them to put them away when company comes over so they are not tempted.  We usually have to keep an extra watch on Jack to make sure that he doesn't touch any of his brother's special items and make sure that we have other options for him to play with.  Many other things attribute to the meltdowns such as television shows, so we allot him a certain amount of time for television to watch what he wants, people talking while he's talking and to curb this we have to explain to most people that he won't finish talking until you let him finish what he is saying, and many other instances lead to the meltdowns.  With this said, meltdowns can not be prevented as they are a way of letting out pressure of over-stimulation or social anxiety, however it is possible to curb the behavior once you learn how your child operates and build a plan to work around them.