Getting a filter stuck on a lens is a quick way to ruin a photo outing or trip. Attempting to remove the filter improperly is a quick way to damage an expensive filter.
The key concept to remember when removing a filter is that even pressure must be applied around the entire ring - otherwise, binding results. You may never get the filter off if squeezing it. Apply a gentle, even pressure and the filter may come off easily. I've handed a lens with a stuck filter on it to someone else who simply screws it off without effort. Yes, it is embarrassing.
If even hand pressure with twisting will not remove the filter, there are many options to try. Some include ... Pushing the filter toward the lens itself and twisting. A flat, rubber jar lid opener may be the solution - lay the jar opener flat on a solid, smooth surface and place the filter down onto it. Twist the fully-retracted lens barrel while applying pressure against the jar opener (taking care to avoid damage to the lens). Another option is to attempt hand-removing the filter while wearing a rubber dishwashing glove. Or the best solution - use an inexpensive plastic Lens Filter Wrenches.
It doesn't seem to matter how careful I am - I still manage to get stuck filters. After getting a Neutral Density filter stuck on a 67-77mm Step-Up Ring while on a recent trip, I finally invested $5 in a pair of Lens Filter Wrenches.
There is not much to a Lens Filter Wrench. It is a light, molded piece of plastic that goes over the stuck filter. Squeezing the two finger extensions tightens the wrench around the filter. While squeezing the wrench tightly, twist to remove the filter. The wrench applies the even pressure concept as it grips the filter.
Circular Polarizer Filters are especially hard to remove. The end of the filter turns by design and getting a grip on the remaining thin non-rotating section is challenging. A Lens Filter Wrench is especially useful in this situation.
Filter wrenches come in pairs. If you have two filters stuck together as I did in my example, you can attach a wrench to each in opposite directions.
Lens Filter Wrenches fit a range of filter sizes - be sure the set you are buying fits the filters you plan to get stuck.
As they are cheap, it is best to order these in a larger planned order as minimum shipping charges can easily be as expensive as the Lens Filter Wrenches themselves. When purchased along with other gear, I think they are very worth this small extra cost.