Appropriate broad-ranging "socialization" refers to the process of exposing
young pups (especially important between their 8th and 12th week) to a wide
variety of experiences, including but not limited to, interaction with other
dogs/pups, humans of all different ages, sizes, shapes and colors, and novel
environmental stimuli. Appropriate means that the pup has only
pleasant/non-threatening experiences during exposure.
Sounds like a tall order, and it is, but properly socializing your pup will
help prevent social sensitivities from developing in adulthood, which is not an
easy thing to deal with.
Below are two excellent articles on the topic. The first is a Position
Statement from the American Veterinary Society of Animal Behavior, and the other
is a great article on why siblings and roommates "don't count" when it comes to
socializing a pup to other dogs.
Check out the achived Tips section on woofology.com for more articles on
the importance of early and appropriate socialization, and feel free to pass it
on to your friends and family!