Avocado's are delicious and very good for you.   They have a high oil content and a light and flavorful taste.  If your Avocado is not ripe, you can put it in a paper or plastic bag with something ripe already to help it ripen.

Disassembly

The Avocado is a very slippery fruit when ripe.  Below is the best way I have found to dice it up.

Take your chef's knife and slice around the pit from the top of the avocado to the bottom going all the way around, making two hemispheres(west and east).  Twist the two hemispheres in opposite directions to separate.  One side will have the pit and the other wont.

Take the side that has the pit in the palm of your hand with the pit facing up and lightly whack the pit with your Chef's Knife using the blade closest to the handle(you'll have more control).

Then with the blade in the pit rotate the pit counter-clockwise so that it comes out of the avocado attached to the blade.

Attention

Do not try to take the pit off the blade by grabbing it and pulling it from the blade.  This is a recipe for disaster!

It's very safe and easy to remove the pit if you follow the instructions below.

Approach the pit from the blunt end of the blade with your free hand. Then pinch the blade close to the pit and slowly push the pit off the blade.  Your palm should be resting on the blunt side of the blade and the sharp side should be facing away from you.  Simple!

Dicing

Now you have two halves of the avocado, pit free.   Do not try to peel the avocado, as this will just make a mess.  Instead take one half and place it in your palm, flesh side up.  Take a small paring knife and cut the flesh of the avocado while it is still in it's skin.   If the avocado is ripe the knife should cut through it like soft butter.   You can make a any grid pattern you want with any size you want.   When you are done cutting, take a spoon and spoon it out.

Done.