If you want your dog to walk nicely then the first thing you must learn is how to properly handle a leash. Many people constantly mishandle their dogs leash and actually cause the dog to pull or act up on the lead.
The following are signs that you could be mishandling the lead:
Your dog bites the lead,
Your dog rolls on the ground when the leash is attached (I call this Death Rolling)
Your dog flips onto its back (I call this a Tap-Out) when the leash is attached
Your dog paws at the lead
Your dog jumps on the lead
Your dog constantly jumps on you when the leash is attached