1. Get Special Promo Codes
Make sure to look at individual sellers' "Shop Announcement" page, because that's where special promo codes can be found. Some shops change up promos every month, while others have discounts during the holidays.
2. Keep in Touch
If there's no promo code, send a message to the shop owner and ask if there are discounts coming up, or ones that aren't posted. It never hurts to ask, and if someone is going to make a big purchase, the shop owner might give the buyer a special discount.