Depends. If you're in a relatively open area and can track them, there's nothing wrong with putting the bullet right in the heart/lung area and follow a potentially minimal bloodtrail to your pig. In thicker vegetation, I prefer to "neck" shoot them. I put neck in quotes because it seems to me that pigs don't really have necks. Anyway, shoot them about 2" below and behind the ear and you'll break the spine, dropping them where they stand. At closer ranges, this is what I like to do. When shooting farther, I go for the heart/lung shot because I like the larger target area on a critter that rarely stands still - gives more margin for error.