What makes a class successful?

Kind of unexpectedly I just got asked to teach a "Flowers in Watercolor" class at the local art center here in our small town. I'm really excited! What a fun, new opportunity. I'm also a little overwhelmed. There are two problems. 1 - I've never taught adults before. 2 - Since I graduated from college, I've never taken an art class. Not a one. I've wanted to really, really badly, but just haven't had the time or money. I've painted lots and learned lots and progressed lots, so I do have things to share. But I can't say I know what makes a good class. I would LOVE to hear from any of you that have taken classes or workshops - good or bad - and hear your ideas as to what makes a class effective and fun. I'm not a methodical painter. I don't have things down to a science. I can't tell you which are the best paints or brushes or which paints stain more, or which colors mix better with which colors. But other teachers can offer that. I don't think I should try. Any suggestions for what I should do? What has worked best for you? I appreciate any advice!! Thanks!!