There are a number of effective ways to immediately increase your direct mailing list response rates.  The immediate and easiest thing to do is to reduce the number of pieces you mail to your direct mailing list that will most likely not respond to your offer anyhow.  This is done by making sure your list has been ordered one per address, not one per household.  If you’ve already ordered your list, dedupe by address and that should cut 10% of wasted mail right off the bat.  You can also cap your targeted direct mailing list by selects.  Many mailers will mail to everyone older than age 25.  But is your offer truly effective for people age 75 or 80?  If not, cap the age range and again, reduce the number of pieces you’re mailing.  You’ll likely going to get the same response, but decrease your expense, and hence, increase your ROI of your direct mailing list.