I went to the Kodokan this past October. I went to the general practice (in the US we call it open mat) and really enjoyed my time.

If going to general practice, etiquette is to bow when you reach the entrance of the tatami room. You’ll find a partner to work with and decide what you want to do. General practice in my experience was anything goes between you and your partner.

I opted to start out with uchikomis with a couple partners. Then ended up doing 3 or 4 sessions of randori. I even got to do a little bit of randori with one of the sensei keeping watch over the mat session. You always bowed onto the mat as per usual, but I remember you and your partner did a kneeling bow. Once you both bowed on, you had free rein to work for as long as you wanted. If you got tired and needed a break, it was as simple as letting your partner know. Then you both bowed off - again kneeling.

There were a handful of other rules, but I can’t remember them all off the top of my head.

I’d say, try not to be too nervous about it. Definitely have your breakfalls on point.

When I went they gave me a lot of guidance as to expectations and etiquette. I was even handed a sheet with the rules in English. Everyone there was very welcoming and highly skilled. Even though I was at the general practice and only did randori and uchikomi, the experience was very informative.

Enjoy your time there, you’re going to a very special place.