I often notice the scary fact that visitors driving here in Japan don't know how to read local road signs. I found a good guide on the internet. Please take your time to study it. You can probably find similar ones by Googling keywords like "driving rules in Japan"
http://www.yokota.af.mil/shared/media/document/AFD-100329-005.pdfhttps://www.npa.go.jp/annai/license_renewal/english.pdfIn particular, I notice that many foreign drivers don't know how to read the speed limit. There are always road signs here and there, so be sure you obey them or at least follow the crowd.
Parking lot systems differ depending on the lot. As it is with anyone driving in a foreign country, it's best to ask if you're not sure. That's what even locals end up doing as there is so much variety!
It is illegal to park in almost every curb in a city. If you must leave your car for one reason or another, be sure you keep an eye on it so that you can run back as soon as you see the police coming. You will be fined right there if no one is there to move the car.
A lot of stores and restaurants give you parking discount tickets, so be sure to present your parking card (which you usually get at the lot) and ask if there is any "waribiki (discount)."
However, in the countryside where there is a lot of space, you can park almost anywhere and most of the parking lots are free.
Do note that driving in central Tokyo can be quite tricky. Even Japanese residents who are used to driving in the suburbs can't or hate to drive in the Metropolitan. Meanwhile, the moutain roads are very curvy and steep. Take your time and drive safely.
All seatbelts are a must according to the law, and the police are quite strict about drivers' seatbelts. Also, you cannot use your mobile phone while driving even at a red light. Be sure to stop your car at a curb when texting or calling.
Strangly, eating and drinking is allowed while driving. Talking on your mobile phone using a headset is allowed too.
Drinking and driving is strictly prohibited not only by law but also by the society ever since there was an infamous accident. Bartenders can also be punished if they provide alcohol to drivers. If you drive to a bar and decide to drink, you can ask bartenders for "daikou" service in which two cars will come to pick you and the car up to be driven home for a fee similar to one taxi ride.
Hope you have fun in Japan!