After you do something in Excel, you may be able to repeat the action by pressing the F4 key.
For example, after you format a cell with bold font, select another cell and press F4. That cell is also formatted with bold font, and it's much quicker than moving the mouse to click on the Bold button in the toolbar.
You can also use the Ctrl+Y shortcut to repeat an action, or click on the Edit menu, and click the Repeat command, as shown below.
