I leave a tip if it was a good experience and I plan on going back.  As a general rule I tip for good personal service, hobby related or not.  In situations where tipping is socially or professionally inappropriate (doctor's office, dentist, lawyer, etc.) I take a small gift on my next visit.  Those situations are pretty clear to everyone; you'd be hard pressed to find a doctor with a tip jar.  But I doubt you'll find many providers willing to argue that tipping is inappropriate.  And nothing says "good personal service" to me like taking a warm facial 

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