Packing Tips Needed

I travel a lot and am a complete mess at packing. Proof of Kirby's packing ineptitude
I leave in 9 days for Germany (5 days visiting Department of Defense schools; more about that later), France (a few days in Paris then on to Giverny and the Normandy Beaches) and finally London (via the Chunnel). Five days of work, a couple days of travel and about five days of play.
Please: share your top packing tips with me!