I teach Illustrator (used to teach Illustrator and PS) first off... an hour will go by like 20 minutes if you like what you are teaching, second most awake students will throw questions at you, so don't feel like you have to have an hours worth of work, keep it simple and have the entire project saved in multiple stages. You never know what tech issues you will run into so if you can make sure version numbers and everything is in place.

If you are lecturing more than teaching, you will accomplish more in your time... I tend to have the students follow along, if you do this expect delays since the slowest person will constantly be behind and will slow everybody down.

Mostly though if you are excited about doing it the students will be excited too.