We live about 1,200 miles away, so a trip to our favorite place is a rather large part of the year, especially because of a certain significant others inability to fly.
Anywhere from about a year away from our trip I usually first create a MSWord document to serve as a cheat sheet. It includes: reservation numbers, prices to expect for tickets/transportation/food/etc., a list of restaurants to consider, and a make-shift park schedule. Then I e-mail it to the others involved in the trip (my girlfriend and my baby sister, ALWAYS), and I ask them to write just about anything they can in a response. Then as the vacation gets nearer things become more concrete. I make the PS arrangements based on the parks we will be in and the group's suggestions and attach an "official" driving page with our directions.
We bring food with us for the drive and inside the hotel (we always stay on disney property), but that is done in the last month we are leaving. During that time we pretty much just pile up stuff we bought, like toothpaste, and call everyone to update them on our status almost daily.