How to make a good Chicken stock?

I made my chicken stock from following recipe taken from shiokfood.
I made the chicken stock and use it in the Tom Yam recipe and the soup turn out delicious!  A lot of soup needed chicken stock so its a good idea to make a big pot and store the rest in the freezer when you want to make other recipe.

Good chicken stock is very simple to make. Take 1 kg chicken wings, throw in a couple of drumsticks for meat, put it in a tall stock pot, cover with 2 litres cold water, and bring to a simmer. When the scum rises to the top, skim to another bowl with a shallow spoon. This should take 10-20 minutes. When the stock is clear, toss in 4 spring onions (scallions; use only the white part), 5-6 slices ginger, and a teaspoon of black peppercorns. Let this simmer for 2-3 hours (it should only bubble). Two rules for good stock: a) do not stir and b) do not boil (or it will become cloudy instead of clear.)