Drink a lot of water, exfoliate your skin once a day and apply lotion beginning 2 days in advance.

Avoid these before your appointment to be sure you are hydrated and your skin is prepped for the tattoo.

Alcohol. Abstain from alcohol the night before, during, and 2 days afterwords.
Time in the sun before a tattoo appointment.
Caffeine can act as a blood thinner.

Limit your guests to one person. Be prepared to sit. Bring headphones if desired and plan on keeping conversation to a minimum unless your artists initiates it to respect the process and guarantee the best possible outcome for your piece.
Have eaten within 1-3 hours.
Brings snacks and stay hydrated with water. Make sure you stay properly hydrated before and throughout your session. A snack for long sessions to keep blood sugar levels from dropping.
Wear comfortable clothes. Remember tattoo placement, so if you are getting a piece on your thigh, wear loose shorts or a dress.
Shave the tattoo area, carefully, the morning of the appointment.