Having perused this discussion to date I have noticed a number of issues brought up are ones mostly for which you, the potential teacher, have little or no control over. I have not been to Pensic for quite a number of years but the problems that have been brought up are not Pensic specific. I have taught many classes in many other venues and have this to offer.
First, be a part of the solution not part of the problem. Get the details of what your teaching together. Practice teaching your class, say at your local group, and then get signed up to teach at the appropriate time that the signing up needs to happen..
When it is time for your class, be there and teach it. Don't cancel. It's a voluntary organization, but you volunteered to teach your class. It is now your obligation and responsibility to teach the class and make it a good one.
Put yourself in the mindset of someone who might wish to take your class. There are times for basic classes like build a 6 board chest, but how many folks want to spend an entire day of valuable war time doing only that? Advanced classes requiring a prerequisite usually don't work out. To use black-smithing as an example, rather than teaching a class on advanced black-smithing, teach one on a single skill like forge welding. Hands on is great. Heating, scarfing, and bending the link into shape, will be more of a struggle for a beginner (He may not even realize he is learning these new skills) but a beginner should still be able to do the forge weld and thus not be “left out” in what might normally be called an advanced skill.
There has been a large “push” “for complete a project” classes where I am from. Doing a small part of a bigger project can often bring a person more satisfaction than a dumb take home project- who would want a single chain link? But I connect them together into a chain for a larger machine and each link is marked and recorded in a notebook so it and who did it can be identified years later. A “Making period glue” class I taught went over really well. We glued together 5 ft long 3 ½ ft wide panels to make bellows. The “students” were involved in a real and important project.
“I don't Know”, can be the most important words you can say in a class. Don't try and BS your way through it. Always have your documentation down. A period example where they did x at this place and this time is indisputable but remember that one example does not speak for every time and place, and there may be other solutions at different times and places.
Make it fun. You are there to teach not be a comedian but the right joke now and then can make a class memorable. Control your class. You have an agenda/outline and time schedule. Stick to it. Some questions should be answered immediately. Sometimes it's better to say I'll get to that in a few minutes. or Can you save that for the Q&A later? Allot for that time.
I have found that a class of about an hour to an hour and a half long with some hands on, that is narrowly and carefully defined can teach more and maintain better interest than one that is too long and too encompassing. Have at minimum a handout with a bibliography of your sources.
Evaluate your class immediately afterward. Was it well attended? Ask your students how you could have made it better. What did they like/dislike? No??: Should “fabricación de cajas “ have been called Spanish box-making? Are you the only one in the SCA interested in African Pigmy dress from 1500 to 1600? Maybe It just was at the wrong time or place for your would be students. Try trying again later.
Your Class represents you. Teach it well. Good luck!