Buy One Get One (or BOGO for short) is one of the best offers you can use to clear out and move inventory and generate more cash. People have to buy more to get the offer, so you get more money.

Some examples of promotions you can create with the Buy One Get One Free plugin:

Buy two products and pay one (2×1), or buy three products and pay two (3×2)
Add a “sunglasses” automatically for free to the cart when the customer buys two “t-shirts.”
Allow the customer to choose for free a product from the “Laptop Bag” category if he purchases one product from the “Laptop” category.
Add automatically one item of the same product that the customer purchased.