Mark your figures with discs
The question often comes up during a role-playing session, “how do I mark a figure on the battle-mat?” Here’s one solution, make discs out of dowels.
For those not familiar, dowels are short wooden rods you find in craft stores or in the craft department of your local super-store (for example Walmart). They come in a variety of diameters, I recommend the 1 inch variety as it matches up with the size of your typical battle-mat grid. While there be sure to pick up some paint as well, 4-8 colors should give you a large enough variety.
Once you have your dowel, cut small sections of it (be consistent with the size) and paint them in different colors then when a character has a particular effect placed on them you can slip one of these discs under the figure. Since the discs are painted you can easily tell which effects are in place.
If you have a figure that’s larger than a single square just slip a disc under each corner of the figurine to mark it.