One of the most powerful tools in my training arsenal is my notebook.
As my training and my travels to my friends schools deepened I began to realize much of what I was experiencing was a one time deal. I was a guest, training when I could in schools that offered deep material and I realized if I forgot what I experienced it might never come down again.
I worked out my own shorthand how to describe technique applications and kata and started taking notes.
I worked up some rules, first wait a few hours or do it the next day. If you can't remember something that long your notes' won't help you. First take the notes with accompanying stick diagrams to be followed with re-writing in greater detail.
So you go from experience to quick visual notes to more complete notes. These steps re-inforce each other allowing you to have a chance to remember the experience and re-create it later.
When video tape became available and friends performing clinics for my students were filmed I found unless you take the time to write up everything it is lost, but if you write it up it will last.
Video tape remains on the shelf, no matter how good the material shown was.
Clinics with great material are a problem. As an instructor at any time I have my students involved in their personal course of instruction with material that follows a pattern. Getting new great material doesn't mean we can practice it at that time. As a rule of thumb I find it takes at least 5 years before I can insert the best of the best into the program. I have to work on it to fully understand what I want to do with it, and the students training needs to be developed to the point where it fits where they are. Solid notes help you prepare.
The instructors who've visited me have shared dozens of forms, hundreds and hundreds of great techniques and applications. Only through notes have I been able to scope and understand what they've shown.
In fact to take those notes you get to watch those videos in detail, over and over, and you get surprised what you didn't see when you were on the floor.
You also need to take notes on what you teach. Analysis and on the spot choices continually find new answers or approaches to technique use. If you don't write it down, a month later the student asks "Sensei, can you re-do that great technique again... and you're lost because you've moved on and aren't there (the situation where the technique arose) at that time.
The power of those notes.
I can recreate techniques I was shown 30 years ago which have never fit my students needs.
I could re-create entire clinics in much detail if I choose, which I don't, but I could.
The time spent pays other dividends. Analysis of detail in one art shows me how the same techniques were already present in my Isshinryu, just not seen from that direction.
A decade later when that friend visits and sees your students working on a drill or a kata exercise tha they had forgotten they had shown you or knew you only experienced once, the look on their face is priceless as they see the reflection of their efforts.
On occasion when visiting a school or clinic when I get home I write my notes up and then send them to the instructor too. Allowing them to see what they showed through my eyes.
If you don't write it down it didnt' happen.