A duct tape "X" on my suitcase is what I use to make it easy to identify on the luggage conveyor. I quick check the ID tag on the handle just to make sure someone else isn't using that method before grabbing it.
With the airlines charging for a second bag (or even ONE checked bag in some cases), I'm using more creativity when packing. Packing my some gear (wetsuit, fins, knives, save a dive box) and clothing wrapped in a kitchen garbage bag has worked ok so far. I usually have a couple extra bags stowed in the suitcase for the return tip. I'll usually throw a couple dryer fabric-softener sheets in too to try to make it smell a little better for the return trip after a week of diving.
Heavier or expensive gear (BP/W, regulators, computers, camera & mask) have been going in my carry on. It's worked fairly well so far.