Who is the target group for your classes? Then find out where they hang out and market to that area. I often search for facebook groups in my area that target my niche group. Or work with other businesses, social groups, etc that include my target niche. You can also think of where these people go to hang out (a bar, coffee shop, etc) and see if you can offer a trial free class at that location to gain interest. It doesn’t have to be a full class, a 10-20 minute teaser works great too.