While sewing may or may not be my forte (jury's still out on that, I think), what I spend most of my energy at events on is teaching. After the first few awkward sessions of sharing what I knew to a group of strangers, I've loved the process of developing and teaching classes on the variety of topics I find interesting. In fact, teaching (and the researching process that goes into being able to teach) is what I typically say I "do" in the SCA. My enthusiasm for teaching, and of course my interest in the topics, drive my teacher personality, and I'm happy to report that I've yet to teach a class that was a dud.
Last week a friend wanted to test out a new class she was assembling, and had asked me to give her some advice and pointers. I listened to her class, and took some notes. Reading back through the notes, I realized that several of the things I'd written down were not necessarily specific to her topic, and could really be great advice to anyone thinking about taking the step from student to teacher at events. In fact many of these pieces of advice are things I've learned along the way, both as a teacher of my own classes and a student in others'.
You've decided to teach because you're interested in the topic. That interest, by it's very nature, will do you a huge favor- it will help you retain information and understand your topic better. So as you teach your class, trust that you'll remember what's important, and be confident that you'll be able to answer your students' questions. You do not need everything written down. Outlines or index cards can help you keep your place and order, but don't use your class notes handout to teach with. I think that most folks who try to rely on fully-fleshed out notes to teach their classes are worried that the beautifully salient points they want to make, which sound so good in writing, will get lost if they don't read them. And while this can be true (it's happened to me), there are ways to remember these well-worded statements without reading the entire content of your class. Repetition, for one, is an incredibly powerful tool. Repeat what you want to say often enough, and when the time comes, you'll recall it. Not only that, but you'll speak it with inflection and intention.
Handle jargon/foreign words as smoothly as possible.
There may be times when you've got titles, names or jargon specific to your topic that you really are better off reading. As teachers of medieval topics in particular, we're also constantly faced with foreign languages. When we can't get through a topic without these words, and we have a genuine problem committing them to memory, we tend to do one of two things. We either say them very quickly with no regard for exact pronunciation, or we slow way down and speak the words syllable by painful syllable. In either case, we've sidetracked the moment and potentially lost our students.
If the words can be translated without losing meaning (if using the original language isn't important), rely on the translation. If the words are important to share in their original language, state the word as clearly as you can, tell them what language it is, then translate it. Then use the translation from that point forward in the class. If it needs to be stated correctly, but you can't get the pronunciation from the original spelling, write it phonetically for yourself. So "Tres Riches Heuers du Duc de Berry" might be written "Tray Reesh Uer duh Dook deh Barry". Again, repetition of that pronunciation will greatly help. If you're not sure about how to pronounce something, do some research on the language and make a best guess, or ask someone that may know how they would pronounce it.
We all like stories. It's part of our human nature to be drawn into them. When your topic is extremely factual information, sometimes creating stories around that can be difficult. Which, of course, means you'll have a harder time keeping your students interested. So instead of just rattling off your information bullet-point style, try forming contexts for the information. This usually involves side research to get more relevant information, such as events, people or similar factors that your listeners can latch onto as "landmarks" as you take them through the data. In some cases, years or maybe culture names can provide all the context they need to place the information for better absorption.
Tell stories with feeling.
When your topic does provide for stories, be sure to tell them! Be personable, add humor if appropriate, and bring your students into the moment. Don't miss the opportunity by sharing the information in a dry manner.
Determine a level of student knowledge for your class.
The specificity of your topic will dictate a certain level. In general, your classes will fall into beginner, intermediate and advanced categories. If we try to teach at all three levels in the hour we've got, we're either not going to get through it, or we're going to find ourselves way off track. We're also creating a situation in which we, as the teacher, may rapidly lose control. I had an experience early on in my teaching "career" of having a well-meaning student sidetrack my class because I'd allowed the class to be pulled into a higher knowledge level than what I personally had at the time. Before I knew it, ten minutes had gone by and my topic had been usurped. If I'd established with myself ahead of time what level of knowledge I was going to teach to, I would not have left that door wide open. After that, I began creating every new class by writing an objective for it. By having a "destination" in mind, I could determine at which knowledge level I was interested in teaching for that class, and I could be better able to maintain control of the class because I knew what I wanted to accomplish by the time I was done. Help your students understand what level to expect with class titles and descriptions that clue them in. If someone with a large amount of knowledge attends your "Beginning Sprang" class, they'll be less likely to take over, since you've made it clear who your intended audience is.
Plan for technical issues.
In most cases, your SCA class won't be taught somewhere with the best audio/visual resources. Even if it does, try not to rely on the available technology to teach, or at the very least, have a backup plan in case the technological assets don't work correctly. I speak from embarrassed experience here.
Embrace the phrase "I don't know".
The best teachers I have had the pleasure to be student to know that "I don't know" isn't a curse of death. In fact, in my own experiences, when I've found myself saying those three words, it gives me a great opportunity to go back and do more research. Also, don't forget that, while you might not know that specific thing, there may be related things you do know. "I'm not sure about X, but I do know Y, so maybe Z is likely, but I'd have to do more research." It doesn't have to be as formulaic as that, but the point is to try not to leave the question completely unanswered.
There are many more things I can share about teaching, but I think these points are the most relevant to share here. Different types of classes (lecture, demonstration, hands-on, etc.) have their own sets of lessons for teachers to learn, as do different topics themselves. I hope, though, that if you're just starting out as a casual SCAdian teacher, you find these tips useful.