Thanks Sandy... Regarding how we get them to sit...
1. I use an easy chair with the background cloth draped on it.
This setup restricts their movement with the arms and back of the chair also providing a background... I probably have twenty pieces of fabric of all types for these portraits. I also use a hotshoe flash bounced and modified with a Joe Demb Flash Diffuser Professional.
2. I almost always have my wife helping me. We use a very light-weight and thin show lead to control the dog - and to prevent puppies from jumping off the chair. I will get rid of the lead in Photoshop with a combination of content aware fill and the clone stamp tool.
But the lead doesn't guarantee a decent picture - I get a lot like these...
It can be a long while and a lot of work. I use squeak toys and treats to get the attention of the dogs. Of course, every once in a while, I am lucky enough to get a ham like this girl who was animated from the start...
Frightened dogs are the worse, animated dogs are great...
I shoot with a Canon 5D Mk.ii and a 70-200mm f/4L IS lens from a rolling office chair which allows me mobility at approximately the height of the dogs...
I need at least four shots for our rescue Internet postings. With some dogs, I get the shots I need right off the bat while with others, it is a long and drawn out process. However, I quit when I see that further efforts will not be productive and will do another session a bit later...
We also like to have props available - sometimes the puppies look cute when the props are used. I didn't like the blue background and have reshot this with several different color backgrounds but, haven't caught the same pose...