Knowledgebase
How to configure the system checkout options in Magento
To configure the system checkout settings log in to the admin panel of your Magento and go to System>Configuration>Checkout button in the Sales section on the left. When you do that several panels with settings will appear on the right.
The Checkout Options panel contains a setting for enabling and disabling the one-page checkout; it's recommended to use the one-page checkout. There's also an option from which you can disable/enable guest checkout, and another one from which you can enable/disable terms and conditions. If you enable terms and conditions, they will be displayed at the Order Review step of the checkout process and customers have to accept them to be able to place the order. If you enable terms and conditions you also have to add them; you can do that from Sales menu>Terms and conditions.
From the Shopping Cart panel you can change the lifetime of abandoned carts. It's set in days and it applies to logged in customers. Shopping carts of guests are cleared after the session cookie expires (one hour by default). From the respective option you can also specify whether customers should be redirected to the shopping cart page after a product is placed in the cart. From the Grouped Product Image and Configurable Product Image drop-down menus you can select whether the parent image of the product should be displayed on the cart page and in the cart sidebar or whether the image of the associated simple product(s) should be shown.
The My Cart Link panel contains an option from which you can select whether the number of all the units in the cart should be shown in the cart sidebar and the header cart link (Display item quantities), or whether the number of the different products (the number of units per product is ignored) should be shown (Display number of items in cart). Using the options in the Shopping Cart Sidebar panel you can hide/show the cart sidebar on the frontend and you can specify how many of the most recently added items should be listed in the cart sidebar.
The Payment Failed Emails panel contains settings which you can use to specify the store email address to which payment failed emails should be sent, the email address that should appear in the From field of these emails, the template to be used for displaying the message. In the respective field you can also type additional email addresses to which copies of the emails should be sent, and you can select the method to be used (separate emails or blind carbon copies).
For more details and screenshots you can read the tutorial on the system configuration checkout settings in Magento.