The best way to stop griefing is to place a protection stone (purchased at the market) where you intend to build, and then ONLY building within the boundaries (command= /ps visualize) of the protection stone. I've always stuck to this method, and have never been griefed.
Sometimes PS stones will glitch and you get griefed anyway. That said, it's better to have the protection in place and risk it not working than to leave yourself completely unprotected on purpose.
