Steal Dead Competitor's Backlinks

One of the easier (and morally grey) methods of building backlinks is to steal backlinks of competitors that not longer exist. Chances are that before your competitor went out of business, they managed to get their product or service talked about in blogs, directories or the press. You can take advantage of this quite easily by making a list of all your competitors that no longer exist and search for websites that mention them. All you have to do then is to get in touch with the author to warn them that the product they mention no longer exists and that they can replace it with your product.