Speak Not Ill of Thine Competitors
Does this require more explanation than the Golden Rule ("Do unto others ..."): Badmouthing competitors diminishes you. Period.
"Win" with better product.
"Win" with better relationships.
"Win" when your industry is prospering and has a good reputation. (Think consultants, ad agencies, lawyers, for example.)
Build up your competitors!
Build up your entire industry!
(And if a competitor is missing deadlines, etc., instead of piling on, say, "Yes, I do hear they're going through a rough patch; but they're a good company and a good competitor and I'm sure they'll sort things out." Or some such.)
Decency rules! (And, paradoxically, the more "dog eat dog" the competitive situation, the more the "decency advantage" matters.
Consider this Comment to my recent Post on supporting one's competitors from Nathan Schock:
"This is especially important for those of us who work in professional services located outside major metropolitan areas. As our entire industry improves in our city, the large companies are less likely to look outside our city for those services.
"Our advertising agency believes that anything that makes the industry better in our city, improves our position. That's why we devote so much time and energy to professional organizations like AIGA, PRSA, and the AAF."