Just relax. Tattoos are really straight forward on the day. Just be polite, be accommodating, make nice conversation as it's needed, don't bring any pastimes that risk the tattooed area move a lot, and don't haggle over price. I honestly didn't use any pastimes for any of mine. It's easy enough to just sit there, listen to the music, make smalltalk, and watch it happen. Also do the usual preparation stuff of eating something, being hydrated, getting there on time, etc. Enjoy it. Tattoos are great.