I've always used a brightly coloured velcro handle wrap on my carry on.
I also have some brightly coloured luggage tags from Inventive Travelware. They have some attitude, and come in bright colours. They're great for sky check- all the black bags come out on the cart, and mine is the one with the green or yellow tag hanging off the edge. I usually put this tag on the same wire hoop that holds my AC Elite card on my luggage.