Test!  Test!  Test!  Even in this economy, it is imperative you continue to test not just new lists but new packages.  Don't get complacent and mail only to the same tried & true lists over and over.  Don't wait until you see your results fall off before you try a new package.  It can take months to get a new package "out the door".  Be ahead of the game not behind it! 

Consider exchanging names with similar organizations rather than renting your entire mail quantity.  Not only will this reduce your donor acquisition cost but you will have access to the most recent and responsive names available.  

Include recent segments of your lapsed donors in your acquisition mailing.  You will not only activate a portion of these donors but you will do it at a lower cost - you're mailing your own names! 

Is the cost of doing acquisition mailings getting too expensive?  Then consider putting a portion of your lapsed donors on the rental market.  Or better still, identify portions of your file, both active and lapsed, that are not mailed to on a regular basis for renewal mailings, and make them available on the rental market.  The more recent the name, the greater interest there will be from outside mailers to rent and the more list income you will see.  This additional list income can then be put back into new name acquisition. 

Mail Multis!  Multis are names that appear on more than one list.  These duplicates, also called multi-buyers or multi-hits, are typically more responsive than the general population of acquisition names and oftentimes will perform at or near the level of core lists.

Join a cooperative database and take advantage of the new innovative modeling techniques to help replenish your donor pool, identify your best prospects and maximize your results.

Hire an outside firm to to an analysis of your file to identify long-term giving behavior.  it will provide you with a complete look at where your development program is, where it is headed and will increase the effectiveness of your fundraising efforts.