We plan it out on the computer. Done it that way ever since road maps became available. We refer to all three of Bing, Google & MapQuest, plan out the trip pretty much to the gnat's behind, and print the whole thing out, with larger (or is it smaller?) detail scale of highway interchanges, etc, so we know exactly where we want to go. Where we feel we need even more detail we'll include satellite/birds eye pictures.
Which is kinda funny. When we travel on the bike we don't have a plan, only a destination. We know the general direction and head that way.