There are several tricks, but generally, it may not be possible to remove without damage to one or both.
The trick to stuck and cross thread filters is to keep the filter round while you turn it. Grasping it with your hand does just the opposite. Filter wrench is your best bet. Any good camera shop will have one.
Here's a trick I learnded a long time ago from a world famous photographer. Put on a tennis shoe, sneaker etc with rubber soles. Make sure the soles are clean. Put the filter flat against the rubber sole and turn the lens. This method keeps the filter round. It works for me when I have a troublesome filter.
Now this is not for the faint hearted but this is how I have done it in the past, not just for me, but also on a friends camera who had a poleriser stuck on for over 2 years!!!. What I do is this; take a knife and gently (GENTLY) insert it between the filter and the threads where the two are only just visible and carefuly prise them apart. You are only asking the filter threads to move a tiny amount to allow the filter to pop its threads back into place. It can be done and I expect many on here will disagree but I have done this a few times with no damage but a freed filter.
>Getting old stinks. I never did this before I crossed >threaded a filter on my 80-200mm. >How can I safely get it off.
The reason it happens (if it was put on properly in the first place) is because of the fusion of metal. Sometimes just light knocking on the filter rim can get in unstuck. Just be gentle. If you have mouse pad put your lens on it filter down and rotate the lens. Soft piece of wood would do the same trick. Another way to do it it put the lens on the hard smooth surface filter down and with the palm of your hand hit the lens rear but not to hard to get thread unstuck.