Askel

That's because there are no clear cut answers on this sort of thing.

When touring for any more than a couple of days, I plan things out as much as I can.

For route selection, my preferred order of information sources:
1. State Bike Maps. Sometimes these are done by the state department of transportation, sometimes by state bicycle organizations. They rock. They usually list shoulder width and traffic volumes for quite a few roads.
2. Adventure Cycling Association Routes. If they go anywhere close to where I'm going, I follow them.
3. Google Maps with street view. Really gives you a good feel for how bike friendly a road is.
4. Trip reports from the internet. Crazy Guy On A Bike is good for this.

I usually make a GPX file with my planned route and load it on my GPS over USGS topo maps to navigate when I'm pedaling.

But I always, always carry a good paper maps with me. GPSen are horrible at giving the big picture and tend to die on me when I most need them.

I'll often use the paper maps to adjust the route depending on weather or anything good I hear about that might be worth checking out. As such, I pick up any free maps I come across on the trip looking for things that might be worth checking out.