Obviously if the gun's not mine, I wouldn't dry-fire without a snap cap, I wouldn't drop the slide on a empty chamber, I wouldn't release the slide using the slide release lever, and I wouldn't slam magazines into the magazine well.
However, note that some guns were meant to take punishment. For example, whenever I invite people to shoot my handguns I always have to remind them not to 'baby' them. For example the formal function check of one of my handguns after I reassemble it, involves dry-firing on empty chamber, dropping slide on empty chamber, and testing of the slide release lever.