Smackaduck's method works fine, but I don't debone my ducks for the grill. What I do is this:
I take a chef's knife (or other large knife) and cut out the back of the duck, in two cuts, one on either side of the backbone. Then, if you are feeling anal retentitve, carefully cut out the ribs and the keel bone. I rarely do this, so I just crack all the ribs to spread the bird sorta flat.
Then. I paint the duck with lard or duck fat, salt it heavily and put on the grill skin side down. When the skin is brown and crispy, turn over and finish on the cut side. This is when you can paint the skin side with a sauce if you want to.
This method is, IMHO, tastier than boning, but it's waaay messier...
I love all of God's creatures, properly prepared.