How would one desecrate or else defile a grave?

Say you’ve got a real monster of a relative who just died, and you want to take one final parting shot. Defiling (or else desecrating) their grave seems like a good way to do it and you’re all psyched up about it, but then you realize:
You’re the latest in a long line of civilized folk. Nobody’s ever taught you how to do it.

Suggestions?

This is not an entirely serious question. I might need the skills one day, but it is unlikely.