This goes back to tipping on carry-out orders. What exactly has the server/bartender/hostess done to warrant a tip? If anything, you should into the back of the house and tip them.
ehh i don't really know. i've never quite known what to do on those... i don't know what they're making. if they're on $2/hr i'd be a total dick to stiff them because of what is essentially the bad luck of getting stuck in the shitty section of the shift. on the other hand 20% doesn't seem warranted.
i generally split the difference and just tip 10%. even for a large order that's not that much money for me, and since they generally get stiffed it usually makes their day. if i made drew brees's salary i sure as hell wouldn't leave a 4% tip.