Usually about a week before we travel we have several things that we like to complete. We verify that there will be a vehicle with hand controls with the car rental agency (see previous post on renting vehicles with hand controls). We do a pre-pack, this might seem unnecessary but trust me it is much better than being in line and being told that your bags are to heavy or won't fit in the machine. Plus it gives us an ideal if we are missing anything (sun block, specific clothing, and the like). Sure you can buy it there, but if you are going to check a bag any way might as well bring stuff you already have. We also make sure to contact our bank, and credit card company to let them know we will be traveling. They will put a travel alert on the card so that you do not have to worry about your card getting refused (plus it is nice to know if my card is used somewhere I am not traveling it will trip the travel warning).
I also like to bone up on the travel books. Also plug travel sites like Frommer's, or Lonely Planet or download APPS into my smart phone. This will save you in the long run if there is a specific place you wanted to go, without you looking like a total tourist (which you are).
I get really excited (and stressed) about this point so these steps are nice to be able to focus on and it keeps me from missing things. Now the count down is really on.