I only recently became aware of the tipping your tattoo artist phenomenon. Like it isnt expensive enough. I try to do at least 15% every session now. If he cuts me a break i usually tip more.

cash is good, good smoke is good, artists who already make a ton of cash I have given gifts, they really seemed to like something personal,
artists got a good idea how much money you make, give a healthy tip and they will take care of you, you are building a relationship, showing appreciation for the extra time, drawing and planning and all,

Mmmmmmm, that salmon looks tasty!

I actually built the armrest that my artist uses everyday. I work in a machineshop and fabbed him up a four legged fully adjustable height and tilt stand. It has a polished coffin front with spiderwebs engraved and clearcoated. I have a better idea for the next one. Got a three hour session from about 4 hrs total working thru lunches and using scrap we had laying around. It was definately a trial and error project. He didnt like the base after about 3 months and i chopped the base mocked up a three leg design that he could rest his foot on. So i got another couple hours free.

I tip around 10% although its not really expected here in Australia. Most decent artists are charging around $200 per hour anyway.

I didn’t tip for my first one as I was unaware of the concept. My co workers gave me a hell about not tipping.
So far I’ve had tattoos from all four artists at the shop (Gallery Tattoos in Camp Hill, PA)
I now tip about 20% and a small bottle of my delicious home made corn or rye whiskey.