Adding a drop down list in Google Sheets is a great way to keep track of specific information or to limit the options that are available to a user. To add a drop down list in Google Sheets, first open a new spreadsheet or select an existing spreadsheet. Next, select the cell or cells in which you would like to add the drop down list. Then, click on the "Data" tab and select "Validation." In the "Validation" window, select "List." In the "Source" field, enter the list of options that you would like to appear in the drop down list. You can also specify the order of the options by entering them in the "List order" field. You can also specify whether users can enter their own values or not by selecting the "Allow user entry" check box. Click "OK" to save your changes.