I have a couple of things to add to these great ideas:
*Take along some water from home or use bottled water. Changes in drinking water can adversely affect a dog's GI tract- not what you want when traveling.
* When I travel with my boys, I always take along a bottle of Resolve pet carpet cleaner along in case of an accident.
Never had to use it, but nice to have just in case.
* Put the Do Not Disturb sign up when you leave. I leave my dogs out in hotel rooms since they are never kenneled and they would freak if I did it on trips. I do move the furniture around using a table and chair to block off entrance to the door, so if someone did come in the dogs wouldn't bolt out the door. I would still use the sign if they were kenneled.