Instructables
video How to cut an avocado (Video)

Press the knife in, until you feel the pit. Then, roll your avocado through the blade until you have cut to and back from the starting point. Press and slide the halves apart. Hit the pit with the knife wedge and once the knife is wedged deep inside the pit hammer it down until you are left with the avocado half. Hammer the pit off by hitting it on the side of your sink.
Great video :) Looks like a very nice and ripe avocado you've got there!