Free Is The Key,
by Alan Rosenspan
You
should always present the offer as something of value and something of
importance. Free is the key. Many people believe that "free" is
the most important word in advertising and direct marketing. It's
certainly the most important word when it comes to describing your offer.
If you are offering something for free-shout it! Almost always start the
headline on the reply card with the word "Free." It will almost
always increase response. Plus, use the word "free" as much as
possible within the other elements of the direct mail package, or within
the advertising copy.
(Taken
from Direct Marketing Strategies)