If you want to work your pup then I personally would want to see working dogs on at least one side of the pedigree, if not both. Many show people do also work their dogs, but unless you know whos who it would be easy to choose an unsuitable pup, one with no real interest in work or a noisy dog, one that sings when excited!
Health tests:- Obviously hip and elbow scored. (There is no point in training a pup just to see it break down with bad hips or elbows!) Hips the lower the better, I put a total of around 10 total (Right and left hip added together) and with only a point or so difference between the two sides. With elbows, only zero will do, 1, 2 or 3 is to me unacceptable. Also I would want an up to date BVA eye test certificate. (These need renewing every 12 months. I can understand if it is a month or so out of date, nobody wants to stress out a pregnant bitch, but no more than that.) With DNA tests I would want at least one side to be clear for PRA, CNM, EIC and preferably also SD2 dwarfism. (I say preferably because although SD2 affected dogs are short in the leg, as far as we know it's not accompanied by any health issues.) These tests are really the minimum I would want to see.
These health tests really are important. The working life of a Labrador can be up to 12 years old and ploughing through the mud or jumping fences is hard work. My Amy was working for her last time at 12 years old, (Although my young Chloe was taking most of the work by that time.) and is now closing fast on 15 years old. (A photo of her below in her young days.)
When I go to see pups I take a knotted handkerchief with me and toss it out a meter or so in front of the pup. I don't expect it to retrieve it, but it's a pointer if it takes an interest in it. As I used to have a breed where deafness was a problem I got into the habit of clapping my hands behind the pup to check for a reaction. Labradors don't normally have that problem, but I still check.
Anything you don't understand, just ask the question and I'll try to answer.