Not quite sure why there is the need to be a great client anyway.
I mean, do you worry what the waitress at gusto thinks of you. Pretty sure my realtor doesn't really care if his clients are assholes or not, as long as they buy a property. And the bank manager only really cares about you taking your money down the road. Why should p4p be any different?
Good clients tend to be good people (and vice versa). Assholes are assholes across the board.
In the service industry there are always what we call PITA guests. Unreasonably demanding, Overly aggressive ...
Then there are guests who will bring up valid criticism in a fair and balanced way. For me, these are great clients.
Oh and have never seen the value of giving gifts to providers (unless you are a regular and it's her birthday etc). Have, however, got a few from providers (as a regular customer), which I would presume to mean I'm a good customer.
And never fall for your service provider. It's just plain stupid.