So far, all I've done is sponge info off everyone else. Finally, something I can contribute!
What follows is a recipe for beer brats that will make you the envy of every other backyard bbq master in your neighborhood, I promise.
You'll need a suitable number of bratwurst. If you can't get it fresh from a local butcher, I've found there are two brands : Johnsonville, and the ones that suck.
You'll need a 6-pack of beer for up to about 20 brats. Local microbrewery puts up a dark nut brew that's awesome, so if you can find something local, give it a whirl. Dark seems to work better, imo anyway. If you're looking for something readily available in stores, my own preference is Killian's Irish Red.
A red onion and whatever spices you may enjoy (I rather like garlic, caribbean jerk seasoning, or perhaps a local blend if you have one you like) top things off.
Drop the brats into a large bowl. Cut up the red onion into the bowl, sprinkle in the spices, and pour in enough beer to cover the whole thing.
Cover the bowl, stick it in the fridge. I've left mine in there for as long as 3 days with no ill effects, though much past 24 hours seems to provide diminishing returns. 12 hours is an absolute minimum, imo.
Fire up the grill. You'll want the heat fairly low.
In a skillet, place 4-5 brats (or whatever fits) and fill about 1/3-1/2 full with the beer/onion/spices right out of the bowl. Cover the grill, and let the heat do its thing.
What you're looking for is to bring the mixture to a light boil and froth, and for the brats to turn a grey color. Should take about 8-10 minutes or so.
At this point, pull the brats out (tongs only please...don't stab em!!) and place them directly on the uncovered grill to brown everything up, much as you might do with hot dogs. The remaining broth in the skillet should be dumped, and replaced with fresh from the bowl for the next batch.
Serve on large split rolls. Offer kraut, mustard (yellow, brown, spicy), and whatever else you wish as condiments, and lots of napkins!
PS - The final grill stage will burn off any residual alcohol, no worries serving these to kids or at alcohol-free functions.