One big thing that we all need to realize when diving is that we are taking something that others make available to take. The owners of stores can easily lock their dumpsters and decide to let it all go to waste but they kindly choose not to. Keeping this in mind you should be aware of what you do around their stores and be respectful in the process. Clean up all and any mess you make around the dumpster. Basically just leave it the way you saw it, except for the treats you are taking home. If you abide by these good dumpster ethics then surely you will have a good relationship with the owners of the stores.
And speaking of treats last night a friend and I were able to score big with over 200 uncooked cookies that will keep well in a freezer!