If you prefer to work with automatic numbering turned off, you can still auto number from the keyboard. 

If you are working in a version of Word prior to Word 2007, select Tools / Customize / Keyboard button.

If you are working in Word 2007, click the Office Button, then click Word Options. In the Word Options dialog box, click Customize in the left column, then click the Customize button next to Keyboard shortcuts at the bottom of the dialog box.

Once the Customize Keyboard dialog box is displayed, follow these steps:

1.  In the Categories list, click on All Commands.

2.  In the Commands list, click on FormatNumberDefault.  (Single click on the first item in the Commands list, then type F to quickly scroll to commands beginning with F.)

3.  Scroll or down arrow to the command, then Tab twice or click in the New Shortcut Key box.

4.  Press the keystroke you want to use to apply numbering.

5.  Tab to or click on Assign, then press Enter to close the dialog box.

Using keyboard shortcuts to select paragraphs, then pressing your new keyboard shortcut is the same as clicking on the Numbering tool.  Press the shortcut again to remove numbering.  You can also press Ctrl + Q to remove any paragraph numbering.