We never tip for concierge services unless it's something really out of the ordinary and requires a lot of extra effort on the part of the concierge. Fixing drinks, printing boarding passes, making reservations at Park or City Walk restaurants, sending out clothes for dry cleaning or repair, for example, all falls under normal job duties as far as I'm concerned. Tracking down a size 10 navy blazer at a local department store to replace one that was lost in transit, arranging for a violin solo at the restaurant for your anniversary, or finding a local jeweler to engrave a memento of your stay before you leave, now that's what I would call special services which would justify a tip.