2 large avocados
2 cloves garlic, crushed
1 large tomato, seeds removed and finely chopped
Juice of a lime
Red onion, finely chopped

1. Run the blade of a large, sharp knife round the centre-line of the avocado lengthways, gradually pressing into the avocado until stopped by the stone
2. Hold one half of the cut avocado in your left hand and with the right hand, gently grasp the other half and twist and lift until the two halves separate.
3. The stone can be removed with a spoon or gently chop the large knife (and it really has to be a decent size with some weight behind it) into the top of the stone (BUT NOT WHILE STILL HOLDING THE AVOCADO IN YOUR HAND, PLEASE!) then twist the knife and, with a bit of luck, the stone will lift out.
4. Scoop the avocado flesh out with a large spoon and place in a large bowl
5. Squeeze the lime juice onto them (this stops them discolouring)
6. Mash the avocado in the bowl with a large fork, leaving it as lumpy as you like.  (Most shop-bought guacamole is over-smooth and a little slimy in my opinion). 
7. Add the chopped tomato and  crushed garlic. 
8. Mix thoroughly. 
9. Turn out into a serving dish and garnish with a little chopped red onion
10. (Bury the avocado stones in the guacamole if you do not need to use it straight away since this delays blackening.)