Hard question... but you should have a set fee in your mind for when this question is asked of you. If you make it on the "high side", and they still want you to do it, you will know how serious they are. The local Community College paid me $20/hour for teaching an all-day paper scrapbooking class a few years ago.
You will also need to set out a lesson plan for each class, as there is just too much to learn in one session. There is so much to consider... and plan... I would rather teach the lessons through a computer store or something like that (which is a possibility for me in the future). Good luck with what ever you decide to do.

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Colleen in Friendly Manitoba...
Proudly selling digital designs at SBB
(Come take a peek at my Gallery or check my BLOG to see what I'm up to)