Here is the hands down, surefire way to cook perfect brats (I know a thing or 2 about this having lived in Sheboygan, the brat capital of the world, my entire life.
First. don't EVER, repeat EVER and emphasize EVER, boil brats before cooking. That will get you seriously injured around here. Also, piercing the brats before cooking is not looked upon favorably
Step #1. Light your charcoal (or turn your gas grill on medium-low)
Step #2. Go find yourself 4 cans of your favorite fermented malt beverage
Step #3. Proceed to consume 2 of the 4 cans of said fermented malt beverage. If you drink really fast, you may need to re-visit step #2 and find 5 cans instead
Step #4. At this point, the charcoal should be ready (or your gas grill should be hot). I always put them parallel with the grill so the grooves in the grill hold them in place. I start with the curved side down. When they are ready to be turned, they will have flattened out which cooking the side opposite the curve much easier. Some people soak their brats in cold water before cooking, I don't think it makes a difference. You will also want a small container of water when grilling to extinguish any flare ups, a few drops usually does the trick
Step #5. Using an aluminum pan or stock pot, pour in remaining 2 cans of fermented malt beverage and cut up some onions. How many onions depends on how many brats you're cooking. I'd say one good sized onion per package. The onions are usually the first to go since people seem to have a thing for onions cooked in beer
Step #6. After cooking the brats on all 4 sides (theres really no formula here, they're done when they're done, just don't overcook them and dry them out. They will firm up pretty good once cooked. When in doubt, make sure there is a tong malfunction which just happens to break one in half. You will be rewarded along with any buddies that are viewing this process.
Step #7. Move cooked brats to aluminum pan which is now full of fermented onion goodness and serve.
Brats go on hard rolls (2 brats per roll) with spicy brown mustard (Guldens) and a heap o raw onion. Some people add pickles and ketchup. Kraut is not very common here, but others around the state seem to like it. If you can't find good hard rolls, a kaiser roll is probably the next best thing. You want to avoid hot dog buns at all cost.
The best brats in Sheboygan come from Miesfelds meat market (
http://www.miesfelds.com/brats.htm) I personally love the Grand Champion Brats and the Garlic and Onion Brats. They will deliver if you are unable to locate them locally