I agree with Dutchyankee. With regards maids an envelope with a thank you on it makes sure they are not accused of stealing. often if i see the maid , i will give $5 direct to her, no confusion, and you know she gets it.
In my view US service has become worse, and tips are expected regardless. I will however tell the manager if service is bad, and that i am not leaving a tip in those situations. Then the server will know to improve.
In many places the 15%, is now creeping up to 18-20% and is suggested on the ticket. Do not tip on tax. Tips also should be in keeping with the effort. involved.