This is such an interesting thread. It got me thinking about our vet and what we like about the practice. The vet himself is alwasy very professional, calm and respectful and always goes into detail to explain and discuss what he is doing or proposing. This is particularly relevant if you have a dog (as we do) with a chronic condition such as arthritis where its management is important rather than looking at a cure.
In fact, it would be interesting to have things like talks at the practice about subjects of interest, such as the management of arthritis/value of hydrotherapy etc. I'm a sad person and would love to go to talks on things like worms/parasites so I could get a better understanding of what they do, how they are caught and why their management is important.
Have a good website - plenty of info on basics like opening hours, what to do if...., costs of basic procedures, bio about key staff, ethos of practice, useful links etc. Seasonal advice useful e.g. reminder about Bonfire Night well before. Love the idea of regular email newsletter, and email queries.
The things I don't like about our current practice are relatively minor but here they are - often difficult to park, especially as it is near a school. Vet nurses are a bit funny - often seem to be more interested in talking to each other than hte customer, and one stinks of smoke, which I HATE.
Toys in the waiting room would put me right off to be honest, although we are generally seen very promptly (another reason why we like them) and have no difficulty in getting an appt.
It would make me run for the hills if you suggested any "woo" but I know some dog owners are gullible fools like that kind of thing - so it might be a case of know your market.
A good noticeboard with info for local dog related stuff such as local rescue news, dog training classes etc. as well as the usual drug company posters about lungworm. 
Like the idea of keeping payment area separate as others have said - it's difficult to juggle dog, tablets, purse, card and debit machine especially when patient is a large greyhound who is extremely interested in the next patient which is a cat!!
I have no problem at all with paying a consultation fee - ours charges around £20. To me, the vet is a professional - even if I come out not needing any treatment I have still needed that professional expertise. However, would not be happy to be charged for a follow up visit for stitches removal - our vet doesn't do this but I've heard of others doing it, and it's a bit naughty.
With my rescue hat on, I've experienced great kindness from vets over the years, who have on occasion substantially undercharged/waived charges for fosters and rescues. I am not for a moment suggesting you should do this, but it's one of the reasons why I have great goodwill towards the profession as I've seen that quite clearly money is not the only motivator.
I'd second the idea of notes on patient preferences/quirks/and possibly other pets. About two weeks ago, we had the week from hell when first one, then two, then all three of our greys were ill with spectacular vomits and poos everywhere. The washing machine was going non stop (we did five loads in one day) and i felt like I needed a season ticket at the vets! Thankfully, every time we went the vet made a point of asking how the the other patients were recovering/doing. We really appreciated that.
Lastly please do tell us what you want from your patients. We are always rigidly punctual and pay promptly, but I ask loads of questions and am very inrterested, I also tend to bring them in/phone up if I am simply not sure about something. Can well imagine vet sighing at PFD type owners! What can we do to help you?