If you are hitchhiking on any sort of a schedule, you’ll need a bit of a plan.
Make sure you check maps for a scale. (A line with measurements.) Otherwise, do not rely on the scale of a map, especially in Japan. Three equidistant landmarks on a map may in the real world be 10 minutes and one hour between, respectively.
Japan uses Yahoo maps, Google maps works sometimes for addresses, if formatted in a non-Japanese way. But reading the kanji for locations of these maps is very useful.
Get a notebook to practice your kanji in. Nice and big so you can hold it up for potential drivers to read. You can get a good notebook and fat marker at a conveni. It`s a good investment.
Convenis are good places to get rides. Talk to people on their way in and out. Be very friendly and polite (obviously) (phrases below). In Japan, many meals are available conveniently. And it’s one of the only places you’ll find garbage cans anywhere in the country.
So, it turns out (at least in Hokkaido) that hitchhiking on expressways is illegal. I made it from Osaka to Hokkaido without issue. Highway patrol (blue uniform) informed me that it is not ok and shortly after told me where the closest highway was where it is ok.
If a car takes you onto an expressway, Parking Areas and Service Areas are great places to go camping. Otherwise, public parks are accessible from sundown to sun-up. Gotta get an early start as a hitcher anyways.
Northern Japan highways have a lovely magazine called Highway Walker that will tell you all the useful features along the way.
All that kanji practice from the maps to the notebook signs will start to look familiar. Spot the kanji on the license plates to see where people are from, and may be returning.
Hitching script. (pronunciation key: one syllable at a time. a=a, i=ee, u=oo, e=e, o=oh)
Konnichiwa. Hajimemashite. Hokkaido ikitai. Hokkaido ikimasuka? Hitchhike dekimasenka? Tochu made demo ok. Sugi michi no eki wa kampiki.
Hello. How do you do? I want to go to Hokkaido. Are you going to Hokkaido? Can I hitchhike (ride with you)? Part way is ok. The next road station (PA, SA) is perfect (to get dropped off at).