Depends on if it's only one class or a series along with the experience level of the students.
If you get to post your subject then wait for sign ups based on your class description, you can just about choose anything you desire to share with others.
If it's a general topics class, you could show the versitality of quilting with a range of projects...quilts, wall hangings, lap robes, walker bags, purses, wallets,etc to get someone to think outside the quilting frame...then give them the opportunity to sign up for other classes on specific topics.
If it is a series, you could do the beginning basics with each week being more difficult knowing the even the most experienced can usually learn something new or being willing to "mentor" someone less skilled.
mmmm...not very specific answer but there is a lot of variables here.
Good luck and most of all, enjoy yourself