You may know that you can right-click on the flag icon at the end of each e-mail you have listed in Outlook. But you can more efficiently set follow-up flags using the dialog box that appears when you press Ctrl+Shift+G.
First, select an e-mail. (Remember to press F6 to make sure you’re in the e-mail plane, then use the arrow keys or home and end to select the e-mail you want to flag.)
Second, press Ctrl+Shift+G, and the Flag for Follow Up dialog box appears. Your cursor will be in the “Flag to” field. Use the up and down arrow keys to select the appropriate flag. Press Tab to flip to the flag color field. You can again use up and down arrow keys to select a color (or use Alt+Down Arrow to see the list).
Third, if you want to enter a due date, press Tab, and type in your date. You can optionally press Tab and type in a time. Then press Enter to select OK (or Esc to change your mind and cancel).
To quickly clear a flag, highlight an e-mail and press Ctrl+Shift+G, then press Alt+C to select Clear Flag. This removes the flag entirely.
To mark an item completed, highlight an e-mail and press Ctrl+Shift+G, then press Alt+O to select the “Completed” box, then press Enter.