One of the best ways to improve Excel skills is to learn how to use its shortcuts. You can use your keyboard, mouse, or touchpad to make a lot of things faster. For example, you can add a comment to any cell. You can use this to write down reminders, notes, or cross-reference other workbooks. To add comments, go to the Edit menu and click the New Comment tab. You can type a comment into the cell by clicking on the "Comment" toolbar.