How early can you palpate puppies in bitch? Or, do you leave it up to your vet?

I let my vet do it.

My sister is a master at this and she says 30 days.

If you are not experienced at this don't do it - let the Vet. You might hurt the puppies they are fragile.

This will be my first time trying it alone, but will still go to the vet for an ultrasound.
You should palpate at 30 days. Much later and you will not be able to fell them. At 30 days they feel like golfballs in the abdomen.

I have to disagree with the 30 days evaluation. That is fine for ultrasounds, but for palpating feti I have always followed Phyllis Holst's info in her "Canine Reproduction" book, which says 21-28 days. I have had very good success with that timeframe. Any longer than that, and the fetus, with it's attendant fluids becomes harder to feel.
Be very gentle so as not to disturb or injure the feti. I use a gentle circular motion along the uterus, with my left hand underneath, and the right hand palpating while the bitch is lying down on her side, very relaxed. It's very similar to a breast self-exam! At 21-28 days a fetus is about the size of a large grape. Think very small water balloon as you are palpating!

I let my vet do it as well and she does it within the 21-28 day time frame.

Each the size of a ping-pong ball. 28 to 31 days but 30 days has always worked here.

In the for what its worth column, my vet wants me to bring my girl in on the 26th day.

I palpate at 28 days, I can usually palpate in about 30 seconds. I have the bitch stand up I stand over her from the front,,head between my legs, take both hands on each side (flat like clapping), and push together and go in circular motion with my fingertips.

I raised rabbits for many years also, and can palpate a rabbit in seconds....they are great learning tools, because you can do it gently and learn to do it quickly. Haven't been wrong in over 12 years.