I'll try to occasionally post some basic teaching tips for HelloWM instructors to peruse here. I teach children from grades 1-9 every day and adults of all ages once per week. These tips and factoids and pointers come from my own experience and the resources I've been given, though they're not necessarily of my own design.
First off, in descending order of importance:
1. Cover the material slowly.
There are some reasons why you might not want to move slowly but in general it's better not to rush through material. Human memory is limited, especially in how much it can store at one time. Psychology will tell you that people will only remember some number of units of information +/- 2. That's a weird definition, but you'll notice it's true as you check for comprehension. Until people start learning patterns in the language (which takes time) they won't be able to group those units of information together and will be severely limited. So don't try to cover more than they can learn. Keep it to about 3-5 points at a time.
2. Keep the class moving at a relatively quick pace.
That's not meant to contradict the previous entry in the least. You should, rather than cover those few points very slowly, try to come up with several activities that reinforce the same few points and keep them going at a good clip. This is to keep people engaged. Think how easily you yourself get bored. Although you love to hear yourself talk, all teacher's do, realize that the students might be interested in what you have to say, but zone out anyway. Lectures can get boring fast, especially if you're saying the same thing five times over the course of ten minutes. Keep the pace up and keep everyone into it, be lively and engaging.
3. Review more often than you introduce new material.
You heard the maxim, Practice Makes Perfect. Well it works with language too. Don't assume your students have learned the material just because you've covered it. Review it at least twice after you've introduced it. There are many ways of reviewing including reinforcement activities, question and response, and various review games. Continue to review material in future lessons. Everytime try to review previous material at least at the beginning. I try to tie in review of previous materials alongside new information. Point out that you've covered it already and people will be more likely to remember it.
4. If you havn't heard your students voices during the lecture, you don't know if they understood anything you said or not- Ask for verbal responses, repeatedly.
Again, don't assume your students have learned the material just because you've covered it. Verbal practice should be a part of every language learning lesson. Have everyone repeat after you together, then individually, then together again. Especially with difficult pronunciations you'll have to get lots and lots of attempts before they're good. This isn't to say that written practice is bad, but verbal practice is easier to assess DURING class/instruction time. Also, I'll go into this more later but use Minimal Pairs to demonstrate difficult pronunciations.