Rework your coals and chips. After about 30 minutes youll notice that the wonderfully aromatic smoke stopped coming out of your grill. Open the grill and blot your salmon dry with paper towels. Remove your grill to access the coals (unless you bought yourself a hinged grill) push the coals together (You may want to add an additional briquette, if theyve burned back, try to keep about the same original mass of burning charcoal) and add another handful of hickory chips. Replace the grill and close it up. Now is a good time to add a few fresh briquettes to your off-grill burning stock, theyll come in handy later.
Repeat as necessary. Every 30-50 min or so check your grill, blot the salmon dry, add some hickory chips and a briquette now and then.