I stab my brats with a fork twice before placing them in the pot. I add enough water to cover and start them on the heat. I put chopped up onion, couple garlic cloves, whole peppercorns and a bay leaf in the mix. I do bring to a full boil (never had any casings burst). I boil for 10 to 15 minutes. Then I throw them on the grill over medium heat and let them get that nice grilled brown on the outside. I try to only turn them over once while on the grill. When they are done they are just full of juice and flavor. There is usually big bubbles of juice in the casings just waiting to be bit into so the piping hot juices squirt you in the face. (that sounds wrong)
I used to use beer, but quickly decided that it was a waste of beer.