Drop-proof your pack
Girth hitch a 60 cm sling to your pack when you’re on a multi pitch.
If your pack has a solid haul loop and the load isn't too heavy, you can use that. (That's one of many things I like about the new Petzl Bug multi pitch climbing pack: the haul loop is extra stout.)
Keep a spare carabiner on the sling. (Here I have a locker; non-locker is probably gonna be fine too.)
When you reach the belay, clip the pack to the anchor, and THEN take the pack off.
Doing this makes it pretty much impossible to drop your pack. When the pack is on your back, clip the carabiner to the bottom of one of your shoulder straps.
Another use for this: if you’re in a chimney or for any reason want to pack off your back in the middle of the pitch. Clip the carabiner to your belay loop, and let it hang below you. (Or, if you're completely done with carrying the pack, clip it to a piece of gear and let your second deal with it when they arrive! =^)
If you have the slightest concern about the strength of the haul loop, you can girth hitch the sling through both the haul loop AND a shoulder strap.
