There are two ways to set up a "How did you hear about us?" field on the customer registration form (which visitors reach during checkout):
1. If you visit Affiliates/New in your Order Management System, you can set up affiliates such as "Google Search", "Bing Search", "Wine Spectator", "Referral from a Friend", "Trade Show", etc.
Be sure you have chosen either "Required" or "Optional" for the "Select Affiliate" setting in Affiliates/Preferences and once you create each affiliate it will automatically appear in the "How did you hear about us?" drop-down.
Because you may be using the Affiliates feature for other purposes, you may not want ALL of your affiliates to show up in the "How did you hear about us" list. For affiliates that you do NOT want to show up in the online store as a selection for customers, be sure to check the "Exclude From Online Store" box when setting up the affiliate.
When setting up your affiliates for this purpose, be sure to read the (?'s) throughout the Affiliates section for an explanation of all of your options.
The order in which these affiliates appear in the drop-down list is alphabetical and cannot be changed.
2. Instead of using the affiliate functionality as described above, you can alternatively create a customer Custom Field called "How did you hear about us?" (Customers/Custom Field blue button at the top). When creating this Custom Field, you may elect to make it optional or required, show it to customers or not, and determine whether customers will be able to write in whatever they want or choose "values" (options) from a list of choices that you control. (For searchable, usable data we strongly recommend that you force customers to choose options that only you control and that they cannot create).
The options for selection by customers are created simply by answering that question in an existing customer record by selecting "new" from the "How Did You Hear About Us" dropdown. If you want to remove an option you would need to edit all customer records that are assigned to that option and change their selection to something else.
When setting up your custom field for this purpose, be sure to read the (?) at the top of the custom fields page for an explanation of all of your options.
When appearing to customers in your store as they are checking out, the options you create will show up in alphabetical order. If you wish to change the order in which these options show up, consider putting numbers in front of them (but this will work only if there are 9 or fewer options).