I have not broken a string on mandolin yet (or guitar for decades) but I do have a quirky ritual. When each string is installed (not to pitch) I wrap the loose ends in small circles then wrap the end around the loop. I also use pliers to pull the base of the loop to seat the string in the post. I do not cut the loops off until at least the next day. Something deep within me says I am asking for trouble clipping them too soon.

Done it that way for years on guitar so I do it that way on mandolin now too. I think it was because I had issues with strings slipping on the posts at one time. I really think that string quality has improved over the years (in general).

Otherwise I change one string at a time and use a piece of tape to hold the loop end on the little claw. I also stopped wrapping the high strings over two claws with the 90deg bend, I just do them like the lower strings. I also lube the nut slots, but not every time.