As you may know, Cross-selling is the action or practice of selling among or between clients, markets, traders, etc. or the action or practice of selling an additional product or service to an existing customer. For Magento, products that are offered as cross-sell will be automatically showed on the checkout cart page before the customer start with their checkout process.
This tutorial shows you how to setup Cross Sell for your Magento store to increase sales
To set up cross-sell products:
In the admin panel, select Product Information on the left and click Cross-sells.
Now the selected products will be showed in Checkout Process as Cross Sell products