Ensure the logo will be clear on any media type without distorting the display. ie: a vertically formatted design will cause a page header to be excessively tall, and if made smaller, the logo text becomes illegible.
Due to the nature of electronic media devices to compress image display to a square as small as 16x16px, ensure that a part of your logo is icon capable to separate and standout on its own. ie: the Target circle can survive without the text.
One Color Friendly
If the logo is faxed or placed on black and white letterhead, it should still be legible without color. So avoid the excessive dramatic art.
If one's business benefits from billboard advertising, the logo should be quickly identifiable by folks who are speeding by.