I have seen and tried a few different techniques on how to remove the skin and seed from a Haas avocado. The one that works for me is below. Another method may work better for you.

Removing the Seeds (Pitting)

• Wash the avocado.
• Hold the avocado in one hand, (stem side--the part with the smaller diameter--being the "top" and perpendicular to your fingers), take a knife with the other hand, then slowly make a cut longwise from the top to the bottom of the avocado trying to keep the knife as centered as possible. The seed should stop the knife from slicing the other hand as long as you do not cut too quickly and are not angling the tip of the knife downward. However, for the cautious, the initial cut may be made on a cutting board then picked up while the knife is still resting on the seed.
• Use the fingers of the hand holding the avocado to rotate it lengthwise keeping the knife firmly against the seed. As long as your initial cut was centered across the length of the avocado then you rotate it fully the cut should end up where it started. Otherwise you may need to adjust the knife some when about to fully complete the cut; the start and end point have to meet.
• Take the two halves of the avocado and hold them with different hands, then twist each half in opposite directions until the sides come apart.
• Place the half of the avocado with the seed in it on the cutting board seed-side up. Making sure that there are no hands or other objects near the avocado half, take a knife in one hand and bring it down with some force on the seed. The knife should be firmly stuck in the seed.
• Pick up the avocado half with the hand not holding the knife, and just like when breaking the avocado apart, twist both hands in opposite directions until the seed is loose enough so that when you pull both hands apart the seed remains stuck to the knife.
• Hold the knife flat and slightly elevated along the edge of a trash can with the seed hanging over the inside of the trash can. Making sure that there is nothing nearby, pull the knife quickly away from the trash can making sure not to raise or lower the knife when doing so. If all goes well, the edge of the seed should hit the edge of the trash can with enough force that it will pull it off the knife and fall into the trash. This is not the safest method especially if there are people around. I just do not like to try and pull the seed off with my hand even though the risk of being cut is probably pretty low.

Peeling

• Hold the avocado with the skin side on your hand and with the other hand take a soup spoon and slide it between the skin and fruit at the largest end of the avocado keeping the spoon pressed against the skin.
• Hold the avocado with the skin side up and close to the counter or receptacle into which you want the avocado fruit to fall.
• Gently slide the spoon further down keeping it pressed against the skin and scoop the fruit from the skin. If you are just going to mash or dice the avocado then you do not have to be too careful, but if you are planning to slice it into strips then work slowly with the spoon and also slide it side to side keeping it as close to the skin on all sides as possible.
• Once the bulk of the fruit is separated from the skin, there may be pieces left behind. You may then use the spoon to scrape any flesh left from the skin.