Picking the correct target is more simple if you've done a good job of cleaning your data.  If you skipped that step, go back and read "Cleaning House, Part 2: List Hygiene."  Hygienic lists are imperative if you want targets that are well focused.  I know that I often want to include as many people as possible, but with well-crafted campaigns, you'll get better response rates than if you go with a broader target.
 
 
