Psychology Today has a great article that explains what your dog (or another dog) is feeling when he/she wags his tail a certain way.
What a Dog’s Tail Wags Really Mean: Some New Scientific DataSpecific tail wags provide information about dogs’ emotional state.
Published on December 4, 2011 by Stanley Coren, Ph.D., F.R.S.C. in Canine Corner
Not yet figured out if when to know they are giving you the five finger salute!