To do:

Watch the tattooist's book to see his work
Follow or at least take into account the tattoo artist's recommendations on size, location, details, etc ...
Once the work is done, follow the tattoo artist's instructions carefully regarding the care of a fresh tattoo.

Not to do:

Haggle. If the price does not suit you, try the competition.
Drink alcohol before, during, or after the tattoo.
Giggling, squirming, screaming, complaining. Clench your teeth and wait for it to pass, it probably will not be the worst pain of your life.
Assume that the tattoo artist will start or finish on time. The lack of punctuality is a chronic disease of tattoo artists.
Go to the beach, the pool, or the sun in the weeks following the tattoo.

Recommended:

If you are happy with your tattoo, let it know.
As at Musing, BNBR stands up to the tattoo artist, his workplace, his colleagues and clients.
In most cases, avoid visible and non-concealable tattoos on the face, neck, hands, etc.
Avoid the names of your girlfriend or boyfriend, the signs of infinity, the portraits of your kids or your dogs.
Do not overeat!