Vets typically feel the ribs around the 4th to 5th rib - near the front-middle of the chest. You should be able to feel the ribs easily, not as though you're digging through jelly. If you can't count 'em...
The abdominal tuck is especially important. If your pup's tummy sags, that indicates excess intra-abdominal fat: "belly fat" that is the most biologically active. This fat is pumping out harmful adipocytokines 24/7. It's hard to get real about our pet's (and our own) weight sometimes. Keep in mind this isn't about looking good in a bikini; it's about staying healthy and preventing serious diseases. Make sure your vet is assessing your pet's weight during each visit.
Definitely check out my book "Chow Hounds: Why Our Dogs Are Getting Fatter - A Vet's Plan to Save Their Lives" for recipes, supplements, exercises, how to choose pet foods, etc.
Thanks for your reply. You may have missed this on the cat weight chart:
"Cats — Domestic short, medium and long-haired"
For a few pure-breed cats, this would not apply.
In the US, the VAST majority of cats are...well, cats: DSH, DMH or DLH. From our national data on obesity over the past four years, there is a strong trend toward much more uniformity among cats than dogs.
The point is, if you're in the US with a "normal" cat that weighs 14 pounds - it's too much! This tool helps illustrate that.