How can i train my dog to not run and pull on the leash when i am on a walk and she sees a rabbit or a squirrel?

First of all you have to always have some treats with you while you walk her. when she sees a squirrel, distract her by calling her name or making a sound so she can come to you. If she gets distracted, then say "good girl" and give her the treat. Another way is to turn around and the other way and call her name and run. Hope that this works for you!

You have to train your dog to be obedient. If you say 'sit' when she starts pulling and she doesn't sit, it is quite simple that she has not yet learned to be obedient. Your dog should be able to sit and stay while you walk away and not come to you until you give the signal. It is all about your dog watching your body language - your dog watches you first and then hears you. Dog Training DVDs could be a usefultool for you to train your dog.