Get a good road atlas, and road maps for every state you expect to go through. Do your basic route looking at the road atlas. Write down the route with pencil and paper, picking the towns and roads from the maps.
Check the state DOT website for construction zones on your possible routes. Re-route if necessary.
THEN use Google maps and satellite view to look at your route options and check for obvious pitfalls.
Maps and Earth are good for checking details but they stink for long-distance trip planning. Sometimes low-tech is best.
FYI you can get road maps from the tourism or transportation depts of the states you are interested in.
