Really, what the trick is is to buy your pails from the same manufacturer. There is no "standard" when it comes to the height, width and taper on plastic pails, so as long as you mix different pails together, you're bound to get some that will wedge themselves together that they will be extremely difficult to separate.

However, if you look in your Yellow Pages under "Containers" or "Pails", you will se companies selling plastic pails in your area. As long as the pails you buy are made by the same manufacturer, they will all have the same taper, height and diameter, so they'll nest together without wedging tightly into one another.

Aternatively, maybe talk to any restaurant in your area and ask what kinds of pails they throw out most often. Then, just as them to throw those pails your way.