Understanding the terms DPI & PPI and what they really mean. Rather than try to re-invent the wheel so to speak, for those wanting more clarification on what printing resolutions they need and how to achieve good quality print have a look at Ken Watson’s web site for how to go about editing photos for printing.
Once you have a grasp of the basic process its really quite easy to select the right image size and resolutions you need for good prints. There will be a permanent link in the sidebar if you need to reference this info at a later time.
Heres the link, All about digital photos.