Here is a
link to a clear, step by step method of stringing pearls
Henrietta Virchick's small book is a classic:
Pearl and Bead Stringing
She teaches a great hand knot method. She also teaches a method with an awl.
It is a good altrnative to the Ruth Poris book mentioned above. It is a little more detailed.
WARNING:
Just about all the methods with links in this thread and both the books- actually show pictures of one sliding the knot with the tweezers- don't do it-
No matter what method of knotting you learn, I do not recommend you insert awl or tweezers into the knot and slide the knot with them- it is too awful to do that on 45 pearls then have the knot slide off and tighten too far from the bead!
RECOMMENDATION:
Whether you use your fingers, an awl or tweezers I recommend one puts the fingers or tweezer through the large loose knot and grab the string right next to the bead and fip it through the hole. Then, keeping your thumb on the bead,start tightening the knot down to the bead. It will go to the correct spot every time.