Mistake No. 1: Ignoring the most important factor in direct mail success. Do you know what the most important part of your direct mail campaign is? It’s not the copy. It’s not the artwork. It’s not even the format or when you mail. It is the mailing list. A great mailing package, with superior copy and scintillating design, might pull double the response of a poorly conceived mailing. But the best list can pull a response 10 times more than the worst list for the identical mailing piece. The most common direct-mail mistake is not spending enough time and effort…