John, his wife Beth, and their four children stayed at a moderately priced hotel outside of Disneyland for 4 days. How much should John tip the maid before he checks-out?

Some professions that provide you with personalized service don't pay well and so they expect a tip - waiters and waitresses, cab drivers, tour guides, hotel bell hops (yes they do still exist in many places), hotel maids, valet attendants (they park your car for you), movers and barbers and hair dressers.  
Often, tips are based on percentages.