How to use Chopsticks
Pick up the chopsticks, which are usually placed on a hashi-oki (chopstick rest) with your right hand. If the chopsticks are wrapped in a hashibukuro, (paper sheath) remove them.
1. Use your left hand to hold the chopsticks. If they are disposable wooden wari-bashi, split them at this stage. I've seen many people rub the chopsticks together at this time to remove hard edges and loose wooden fibers, but it isn't polite, as it implies the chopsticks aren't smooth enough for you.
2. With the support of your left hand, hold the chopsticks by placing them between your right thumb and forefinger.
3. Fix the lower chopstick between the tip of your middle and ring fingers. Place the upper chopstick between your index and middle fingers. Press both chopsticks in place with your thumb.
4. By moving the upper chopstick with your thumb, forefinger and middle finger, pick up a morsel of food between the pointed ends of your chopsticks and carry it to your mouth. Remember, only the upper chopstick should move. The lower one stays put. It's customary to keep your left hand under the food as you bring it to your mouth, in order to catch any juices or in case the food drops.
5. If a piece of food is too large to eat in one bite, don't cut it with your chopsticks. Simply bring the whole piece to your mouth and take a bite, returning the remainder of the food to your plate.

Drinking Soup with Chopsticks
The Japanese don’t use spoons to sip soup and other liquid dishes. Simply lift the bowl to your mouth and sip. It is perfectly fine to use your chopsticks to maneuver food to your mouth while sipping. In the case of noodles, where the soup is extremely hot, it's customary to suck in air along with soup, which makes a loud slurping sound. Slurping shows the chef that the soup is hot, and announces your appetite and appreciation of the dish.However, I should point out thay I myself have never been able to do this comfortably.

Things to Avoid
There are several things to avoid when using chopsticks. Some of these are esoteric, while others are self-explanatory:
Sashi-bashi Stabbing food with your chopsticks
Hiroi-bashi Passing food from one set of chopsticks to another. This is due to a ritual during funerals, when family members pass bones of the deceased
Tsukitate-bashi Sticking your chopsticks vertically in a bowl of rice. Again, this stemmed from a funerary ritual
Sashi-bashi Pointing at someone with your chopsticks
Mayoi-bashi Waving your chopsticks over the choice of dishes spread out in front of you in an indecisive manner
Utsuri-bashi Picking up food with your chopsticks, then changing your mind, picking up something else
Koji-bashi Digging out a piece of food from the bottom of a dish, instead of from the top
Saguri-bashi Stirring your soup, searching out your favorite ingredients
Tataki-bashi Drumming the table or plates with your chopsticks. (Although I admit that my dad used to amuse us with his drumming when we were little! He was always careful to explain, however, that it was bad manners)
Yose-bashi Moving dishes or plates with your chopsticks
Namida-bashi Dripping liquid from your chopsticks while carrying it to your mouth. This is where the left hand underneath comes in handy