One of the most common behavior problems that people have with their puppies
is pulling on the leash. It is much easier to prevent the problem than
to have to correct it once it has become a habit. There are several training
methods you can use to teach your puppy the right way to walk on a leash. 
Slack leash method
A regular buckle collar and
a six foot leash are required for this training. The first step to teaching
loose leash walking is to keep in mind that
leaving the house on a leash is a reward. Secondly, remember that if you
continue to walk while your puppy is pulling, you are, in fact, teaching
your dog to "Mush."
First, put the collar and leash
on the puppy and stand in one place. Give your puppy enough leash so
he can walk about four feet from you. Reward
your puppy every time the leash goes slack. This method is best when teamed
with a reward marker, like "yes" or a clicker.
When
you are ready to begin walking say "let's go" and take a few steps. Chances
are good that your puppy will begin to pull immediately, so plant your
feet and stop walking. Wait for the leash to go slack, give a food reward
and try walking again.

Try
not to yank or "check" the
leash, which is a natural response. If it is difficult for you
to stop "checking," put your leash hand in your
pocket. You should also try to be very vocal with your puppy. Puppies
have a very short attention span, and talking in a high pitched voice
will help
your puppy keep his attention on you.
Donkey and carrot method
A second method of
teaching your puppy not to pull is what I call the "carrot
in front of the donkey" technique. Start walking while holding a treat
in one hand right in front of your puppy's nose. If you have a small puppy
you can accomplish this by taping a spoonful of peanut butter to a dowel
or yardstick and dip the spoon down to allow your pup to take a lick now
and then. Make sure to reward your puppy every few feet for staying with
you. Try taking a single ration of kibble with you on the walk to measure
how well your pup is doing. If you run out before the walk is over, then
you know you have to keep trying. If you find that you have food left over
you know that you are well on your way, and can give the rest of the meal
as a real live reward.
With
either method, do not attempt the training if your puppy has not had a
chance to burn off the energy he has from being crated for several hours.
Have playtime first, and then walk when the puppy is a little more mellow.
Do not get the puppy too tired though, or he may not be very attentive.
When you can walk your puppy and hold the leash and a glass of water in
the same hand you have mastered loose leash walking!