First, pick a ripe avocado you want to use. It should be nicely colored like this one
Then slice it in half. To remove the pit, tap the pit with a sharp knife, then twist the knife and the pit will twist right out. Be careful.
If you want to remove the fruit from the shell in one piece, just take a soup spoon and run it between the skin and the avocado pulp. It will come out in one piece. Most of the time I want to either slice or dice it. Hold the avocado in your hand and CAREFULLY slice one way, then crossways. You will get a nice diced look. You can also do this by placing the avocado on a table or cutting board if you prefer not to cut it while holding it.