If you intend for your playmat to stay in one place, as opposed to taking it apart each time you use it, here is a great trick!  

Assemble the playmat and tape the seams of the back side - turn it right side up.  Packing tape or duct tape can be used to keep the pieces together.  This avoids any potential shifting.

If you are using the playmats in a higher traffic area or have an especially active toddler, having the playmat pieces affixed to each other can be useful.  Businesses who use the playmats should definitely try this.  

What are your playmat tips?