I also find that if I want to do any kind of promo (like at Christmas or Mother’s Day) it helps to know your customer base…. 85% of my sales are woman buying gifts for other people.
Because of this fact the promo that actually works best in my shop is when I offer a free gift, like a pair of earrings, when the buyer spends more than a set amount. I think this works well because they were planning on spending the money to buy the gift for their loved one anyhow… and then they get a nice gift to keep for themselves! Sometimes it is just that little deciding factor
Check out more creative way you can promote your Etsy shop over in the Etsy forums.