One method or test you can use to determine the true disposition of a pup is to pick him or her up and cradle them in your arms, on their back. If the puppy just lays in your arms and makes no attempt to get up-righted he may be too docile to make a good field dog. If the pup struggles and fights and yips until he can get away he will likely be too high strung to train properly. If the pup struggles for awhile and then settles down for a good belly scratching it is a good sign and shows that the pup has some drive yet is willing to be trained.
Remember, when choosing a puppy, there are several methods you can use but none of them are fool proof, except one, your heart. When you are looking at pups and one of them sticks out from the rest and it just feel right, take him or her home. Forget every test or sign you have heard about and enjoy the dog. Even if they never develop into a good hunting dog you will still have made the right choice.