You will need
  • computer;
  • - access to the Internet;
  • - e-mail.
The most common form of failure - silent. As soon as it becomes clear that that candidate is eliminated, he simply stops communicating. If he initiates contact himself, politely explain that, unfortunately for him, it is more appropriate was another contender.
As failure can often be treated and the phrase "we'll call you" is the transition to the formalization of relations after the final stage of selection.
Less common variant of refusal when all the applicants who were not selected or those who dropped out in the final stages (this is more common, as it is too large, the total who responded to vacancy) is sent to (but not in the order of spam: each personally) a message indicating that the preference given to another.
This is usually a standard form: candidate thank you for your attention to the company, I regret to inform that the made a choice not in his favor, and wish you success.
In this "resignation letter" can be used the phrase that the candidate addressee can be considered by the company in the future. Everyone understands that it is not binding and basically means nothing, not this is more than a courtesy.
However, it may be otherwise. Even when the choice is made, there can be no assurance that the selected bidder will take root in the company. In this case everyone who is professionally engaged in selection of personnel, keeps on hand a pool of other applicants. And the phrase this may mean that the eliminated candidate are included in it.

But even this does not guarantee anything.
So the question is, to use this way to sweeten the pill or not, is left to the discretion of each.