Needles, ink caps, ink, ointments, gloves, stencils and razors. The artist should open a fresh set of needles and tubes in front of you this means that they should be individually packaged, dated, sealed and autoclaved.
Choose what you like it will be there the rest of your life. There are so many ways to choose your design you can browse the internet, you can choose one from the flash (art designs) at the shop, or you can bring in your ideas and have it custom drawn for you. But don't ever tell the artist to do what he wants (chances are you won't like the same things they do, and you’re the one wearing it for the rest of your life).
The location is always a major factor (from real estate to tattoos). So give the location of your tattoo considerable thought. It is there forever; don't just think for today think for the rest of your life. I personally think tattoos should be placed somewhere that can be covered and that way you never have to wonder if that tattoo is what kept you from getting that job you just interviewed for.
No, not only is it against the law to tattoo someone that is drunk, but it will cause you to become dehydrated, you will bleed more and consequently have a negative effect on your tattoo.
Pick a day when you have plenty of time, never rush your artist. Eat before you come. Keep some cookies in your bag. Bring along a friend if you need. Let your artist know if you need a break. Ask questions if you have any concerns. Most importantly be as still as possible while on the chair.