15% is regular, 20% for exceptional, 10% for alright.. and NONE if you're a complete jerk, get mine and everyone elses entire order wrong and then accidentally spill coffee on me! ..I'm not bitter.
i give as of lately 10 percent on most cases 25 percent if i really like the service some are very nice and some do not need a 2 percent tip but it really depends on the person .