If you might want to keep a couple of gilts to breed from make sure the litter has been birth notified and that the gilts are suitable for breeding (good conformation, including the correct number of teats), as well as correctly fed and housed while growing. I suggest going to a high end agricultural show (Great Yorkshire, Royal Three Counties, etc.) and wandering around with a pleasant expression with a view to talking to as many keepers as you can (don't do it just before they're due to show, however!) These keepers are likely to have animals raised to a very high standard of stockmanship and well handled, thus avoiding some of the problems mentioned in posts above.