Rewards programs are another great way to get free products. The Sephora Insider program to receive free products when you've spent a certain amount of money.
A few of your favourite brands will reward you for helping them recycle packageing, including MAC, Lush and Kiehl's. Lush allows you to trade in five empty and clean pots of product to get free Fresh Face Masks, while MAC's Back to MAC program will give you a free lipstick (any colour you want!) for returning six MAC primary packageing containers either in store or through the mail. Kiehl's allows you to turn in 10 full-sized bottles of their products in exchange for a travel-sized product.
Image Source: MACcosmetics.com