Our 9 week old GSD constantly bites and chews on our hands and feet... whatever is available. How do I correct him for doing this?

I am a first time dog owner, and I was directed to your site by the breeder I purchased my now 9 week old german shepherd puppy from. I just ordered your 8 week to 8 month video for my puppy, in the meantime I have questions I need answers to. I want to know how soon does a dog start showing dominant behavior? My puppy (Rex) constantly bites and chews our feet, toes, legs and whatever he can get his teeth into, I know this is normal for a puppy by reading diff rent articles on your web site., and I have given him toys to chew on and everything, but he just prefers me or my husband. I want to know what is the correction we should use for this? We have popped him with our hand before, but I just don't want him to be afraid every time he sees our hand, because he drew away from me like he was afraid a couple of times after that type of correction ,and we were only petting him. Like I said I am completely new at this, but I love my dog and have always wanted a GSD, but I do want a well trained dog.