Reservation for hotels and ryokans?

Hi everybody,
I will be flying for firts time to Japan end of August, and up to now I have reserved only my hotel at arrival: although thanks to you I have already a planified route, I still have not booked any other hotel or ryokan.
Do you suggest to do so or can I just do it from there on a day-by-day basis?
Thanks!

End of August is still school holidays, so if I were in your shoes, I would book accommodation, particularly for "ryokan" - if the ones you are talking about are for real traditional inn where they serve meals in-room - then they tend to want booking in advance, with guests arriving at 5 or 6 pm or so in time for dinner.

Also, unless you prefer complete freedom of itinerary to the comfort of knowing I-have-a-place-to-stay feeling, calling each day can be a hassle and take time away from enjoying the day's travel, I feel :)

Travelling in Japan is waaaay better if you get your rooms sorted out in advance. Turning up and asking for a room for that night really isnt the done thing in Japan, esp for ryokan. Also some hotels/ryokan can get a little flustered when they have foreign visitors, but if you book in advance this will give them some time to prepare and there is more likely to be a member of staff who speaks English around during your stay. Have a great trip, but get your rooms booked up - it'll make the trip even greater!