Lamar,
I post the images on my website and give the owners a card with the website address and tell them to check it out. I know most of the people -- and all of the dogs
-- so I can always remind them the next time I see them and ask if there's something special they'd like to see.
I don't go from dog park to dog park in Orlando doing the candids. I stay in my own "home" parks where I bring my own dogs and so nobody is pressured into buying but if they see something they like, they do. Also, it's a good way to get formal portraits once the dogs demonstrate their love for "Uncle Jim". Having Dr. Doolittle hands doesn't hurt.
Jim