After slicing your avocado in half, twist the halves so that they separate as shown above.
In a whacking motion, take your knife and dig it into the seed so that the blade is wedged. Twist the knife to loosen the seed from the meat.
Once loosened, lift your knife and voila! Be careful, gripping the seed with your bare hands might cause injury, b/c the knife can slip, use paper towel to grip the seed and remove it from the knife.