There are Garmin bike GPS computers available but they cost 600 dollars. There is no point getting one of those if you have a smart phone. You could take a car GPS but they are not much use either. Since they are designed for cars, they will always want you to go on the interstate. Standalone GPS devices usually are not connected to the internet so you can't search for specific businesses. Google Bike Maps is hands down the best way to navigate by bike. It always finds the most scenic and bike friendly way from point to point.
Paper maps of an entire state do not have enough detail to show the small roads best for cycling. Often people cycle on busy highways even when much nicer back roads exist because they are afraid of getting lost on the back roads. This is not an unfounded fear. I would not venture off the highway in an unfamiliar area without clear directions.
Go to Google Maps and look up bike directions between Madison, WI and Chicago, Il. Google Maps wants you to make 218 turns in 175 miles. The directions are so complex that following a blinking dot on a cell phone screen is the only way to stay on course. And you should follow these directions. Google does a good job of putting you on the best bike paths. The directions from Madison to Chicago are almost entirely rails to trails paths. They were beautiful. Often the trail disappears and reappears a few blocks away. I would not have made it from trail to trail without Google.
Google Maps worked beautifully in every part of the country except for Montana and South Dakota. Those areas are so sparsely populated that the interstate is practically the only road there is. There is, however, a vast network of gravel roads but you don't want to go on them unless you are a glutton for punishment. We once got stuck on a gravel road for ten miles. It was 100 degrees and the gravel became so large and thick that we had get off and walk our bikes. One trouble with Google Maps is that you can't tell the difference between gravel and paved roads. Google will try to make you go on the gravel roads. Don't listen to it. It is legal for cyclists to ride on the interstate in these states because of the lack of alternate routes. Fortunately Google bike maps are peachy keen in every other state.
This might only work on Android phones. One of the kids on the tour had an iphone and her Google Maps app only had car and walking directions. Walking directions work okay too though. Bike and walking directions are usually similar.
In this instructable I will start with the types of Smart phone touring which require the least amount of tinkering to types which require building your own battery. Anyone can navigate by smart phone. It is a completely different cycling experience.