Adding a drop down list in Google Sheets is a great way to keep track of data and to make selections easier. You can add a drop down list in a cell by selecting the cell and then going to the "Data" tab and selecting "Validation." From there, you can choose "List." This will give you a box in which you can type the items that you want to appear in the drop down list. You can also choose the "Source" tab and select "Sheet Name" to have the items in the drop down list come from a different sheet in your Google Sheets document.