I was a Butcher, many years ago. Best way is to get a very sharp knife, with a blade no longer than 2-3 inches. Keep the tip of the blade as close to the bones as possible, and try to run the blade along the bones rather than "hack" at them, as this will help the meat to come off in a cleaner piece. Run the knife along, turn the bone a bit, run the knife again, etc.. Legs and thighs will be the easiest. Just run the blade down the top of the ribcage on either side, trying to avoid cutting through the ribcage. Good Luck.