Congratulations! You will LOVE this trip!!! Another colleague of mine went in Oct....unfortunately she had some bad weather. Ours (Nov) was picture perfect!!! Only one evening of rain! Sun and warm the rest of our visit!
I used the suggestions from JFMF for packing. I probably overpacked, but I did not do laundry there like many of the others!! I purchased clothes that did not wrinkle (Chico's Travelers brand is one that another teacher bought....I just wadded up the clothes when I bought them and hung them at home to see if wrinkles dropped out before packing them.....many fabrics work great now!). I also made sure I had low pumps that were comfortable. I wore them to school several days to be sure.
Be sure to pack some extra gifts. I know it's not recommended, but we did give our prefecture guides gifts. Our group pooled what was brought and gave it as a group gift as some did not bring gifts. The schools loved receiving our gifts, too....such as pencils, CDs of our schools, etc....I brought freebies from my school district for that.
Your home stay will be wonderful. Mine was quite interesting as it was a single woman who had a German foreign exchange student (who spoke English, too!). If you can email your home stay family prior to going, do so...it helps.
Hot Springs were wonderful for many. No one felt compelled to participate if they didn't want to. Very low key.I brought 2 pairs of slippers....didn't really need them. I imagine you might in some circumstances....one should be plenty. Most bathrooms have "bathroom" slippers that are plastic (one size fits all...these are shared). No big deal. Most bathrooms have at least one "Western" toilet (like ours). I only had to use a Japanese toilet once when there wasn't a Western available. The hotels are lovely!!! Even the "businessman's" hotel in Uji City, Kyoto was fine. Simple, but fine. Hotels in Tokyo and Kyoto were top-notch!
Pack some flat wrapping paper in the bottom of your suitcase along with a small roll of scotch tape. Scissors in your checked bag is helpful, too. I bought a pair in Japan (cheap enough) and brought them home.Don't obsess about gifts. Apparently, what you purchase for educational purposes does not get declared on the forms. Someone will explain this to you there. I brought back tons. In general, we were wisked through things. Some did get checked upon leaving Japan and arriving in U.S.the first time (Port of Entry).Bring some thank you cards.If you can pack an empty suitcase in one of your bags it's great for the return trip!! You'll have an extra bag to bring gifts. It's also helpful when you pack for your Riokan overnight and homestay (a small bag is needed).
I'm sure there's more I could tell you, but this seems like a lot already!!! If you have more questions....just ask.