Tips for Teaching Astronomy
Stay current. Astronomy is a field that changes and updates regularly. Double-check every fact against several sources and make sure you're teaching current information.
Use Wikipedia. It's definitely one of the most useful tools for finding and checking facts about astronomy. If you can't or don't want to use Wikipedia with your students, at least consider it as part of the mix in your own learning and class preparation.
Consider night-time activities. Telescope viewing or even naked-eye stargazing can be a successful activity. Be realistic though and understand that it doesn't always work. With telescopes it's essential that you have an experienced operator - it's not something you can pull off after just reading the instructions.
Things to teach
Explain that we know a lot about how the Universe works but there's also a huge amount we don't know. Scientists use telescopes, spaceships and other tools to learn new stuff, and we're learning all the time. This is a good example of how adults continue to learn throughout their lives, and how the results are exciting and beneficial to humanity (e.g. new technologies derived from space research, etc).
If there's one thing that all students should lean as soon as they're old enough, it's the basic structure of the Universe. It goes like this:
We live on a planet, that is part of a solar system, that is part of a galaxy, that is part of the Universe.