WooCommerce can suggest other products to increase the size of each order.

Two techniques

• Cross-selling: offering complementary products in the cart — a case to go with a phone, for instance.
• Upselling: suggesting a higher-end version on the product page itself.

You set these suggestions up in the “Linked Products” tab of each product.

Key takeaway: used well, these suggestions raise the average order value without feeling pushy.