I just won my first champion brewer of show with the help of my Weissbier. It came second in last years Australian nationals, so it's not a bad beer, though I'm still tweaking.
I use wheat malt, pilsner, flaked wheat and carahell. I've always used a touch of munich but I'm experimenting with biscuit next instead. 12 IBU's of Hallertauer Mitt. I don't like anymore than that, and the one time I entered one at higher IBU it got marked down.
44C/63C/70C/78C mash schedule. I do one decoction after the 60 minute rest at 63C. Then 90 minute boil. There's a lot of advice on the net to ferment cool, but it makes a very clean beer in my opinion. I pitch 3068 at 20C and raise it to 22C after 3 days and that makes a really character filled Weissbier with a good balance of flavours.