As mentioned, some of the seminars in the UK were shorter than I like, shorter than my standard lesson plans. On arrival, I didn't always know how many people would be there, the backgrounds of the students (how many force professionals versus experienced martial artists versus beginners, etc.) what the facility was like or what equipment was available. Traveling, I can rarely carry the amount or type of equipment that I like, so I'm dependent on what can be provided.
Teaching on the fly is a challenge, and I enjoy it.
Make a lesson plan. Don't expect anything to go according to the plan, but plan anyway. I don't remember who said it, but "plans are generally useless, planning is essential." It's a good exercise, it allows you to put thoughts in a logical way. Don't fall in love with the plan-- at one venue I had a tight 'essential elements of self-protection' plan but the students wanted restraint & control. Know your stuff well enough to switch and improvise.
Keep the end-user in mind. That's the students. You are teaching not just to the students but for the students. Not for your ego, not for your pocketbook. If they need something different than you planned, their needs trump your preferences, at least in my philosophy.
There are three elements (probably more) that determine what is possible to teach.
#1: The student base. You have to be able to size them up quickly. Watch and listen. I start with the one-step drill because you can see how well they follow instructions, get a good gauge of any training artifacts or bad training habits that are endemic, find the blindspots... and it engages them immediately.
If there is a wide range of students, your drills should be designed such that beginners and advanced practitioners, pros and hobbyists all will get good value. Their goal is to learn and improve. Once you understand the core of your own skills, you can set the game so that each person can learn what they need. That's one of the differences between teaching techniques and principles, or teaching subject matter and students.
#2: The equipment. Some things can't be taught without the proper equipment. You can't do scenarios properly without armor. Some of the academic stuff (like violence dynamics or force law) are damnably difficult without a white board. I wouldn't try teaching ConCom without a projector, too easy to go off on tangents. Power generation requires firm kicking shields and, ideally, telephone books.
That said, there are other things that don't require equipment-- learning to move a body; or leverage; or targeting. There's more than enough information to fill a day even if you don't have the right equipment. Just don't fool yourself into believing that anything is good enough or complete enough. Targeting is cool, but good targeting with poor power generation is likely to fail.
#3: The facility. My least favorite place to play is a nice, clean, flat place with good lighting and padded floors. It's excellent for some things, but difficult for others. It's hard to do environmental fighting in a dojo. You can usually break off small groups to the office and the restroom, so not impossible. But I like having stairs and access to a few parked cars that are already scuffed and dented as well. In general, you want to do your rolling on mats, but a couple of times a year (or at my seminars) I want people rolling on asphalt, concrete or hardwood floors. I want them to remember that in the real world, stuff is dirty and it hurts.
You can teach body mechanics almost anywhere, but the combination of exploiting momentum and "gifts"is hard to teach in a pristine, flat, uncluttered world.
You also have to evaluate things for safety. Boots are good. If you wear boots you should practice in boots. Mats are good, they make learning to take falls easier. Mats and boots together can result in some really horrific knee and leg injuries. That's bad.
What is the Speed of Dark? - If you are wondering what this has to do with martial arts you'll have to watch till the end. https://www.youtube.com/watch?v=JTvcpdfGUtQ
10 hours ago