I teach, so one summer I decided to ride cross-country. I did that two summers in a row; WA-ME one year, and CA-GA the next year.
I had thought of doing the Alaska-Tierra del Fuego trip, but a friend wanted to do another cross country ride. I did that ride, WA to ME again via northern Canada, and then continued on to FL, CA, and AK.
Most of the preparation for each trip was just a bit of extra riding in the months building up. These months-long trips are actually easier to get ready for physically than week-long trips, because you can take the first few weeks easy and use the first part of your trip as training.
I slept outside in a tent. There are places to hide a tent and a bicycle everywhere, and if you're stuck you can almost always find someone willing to let you pitch a tent in their yard for the night. Although that gets interesting sometimes...
The trip was 1998-99. With the advent of e-publishing, I have it on the back burner to publish the account in the next few years. I'd like my kid to be able to read it someday.