Cut a cedar plank to fit your barbecue grill. You won't be saving this, so no need to be fancy. (We usually get a 1"-thick, 12" wide board and cut it into appropriately sized pieces.) Completely submerse the cedar plank in water for 15 minutes.
Put the salmon"skin-side" down on the wet plank. (Remember that anything hanging off the side of the board will burn, so try to maneuver the salmon all onto the board.)
Salt and pepper to taste.
If you have a favorite herb or spice, you might want to add a sprinkle now.
Pat a thickish coating of brown sugar evenly over the top of the salmon. We like our salmon well-glazed, so we pat about a 1/4" layer onto the fish.
Dot with little chunks of the butter, use more or less to your taste.
Grill (on a rack) above medium hot coals for 20-30 minutes or until internal temperature reads 135 degrees.
To serve, just pop the plank onto a platter and cut pieces off the salmon at the table.