I am by no means an expert, but I have found that teaching the come command is the most important you will ever teach. One thing I do know is that we have a tendency to make come to a negative rather that always a positive. We tell them to come and them we make them come inside when they were having so much fun playing in the yard. Or we make them come for a bath that they hate. I also think we overuse the "come" command. The "come" command should be a no holds barred command and should be used sparingly. IMHO I like to use "here" for the unimportant "I would like you here please".

Whenever you use it - make sure it is a very positive experience. Have your dog come and reserve the very best of treats when the comply. Have your dog come and treat him to the best belly scratches imaginable. The "come" command should always be a positive experience. What I found myself doing is using "come" when I wanted Leo to come inside when he was having so much fun running after the birds. It didn't take him long to start ignoring my request. So I starting backtracking and using the "come" command for juicy treats and more play time.

After a few months of that, I started tapering off the treats - but I still use them on occasion so he is never sure if he gets goodies or not.