Bloodborne diseases are no joke. Hepatitis and MRSA are easy to spread if conditions are not clean and procedures are not in place to avoid contamination. The following list of ways to protect yourself comes from the Association of Professional Tattooists website. The simple rule from the site is first. My addition or explanation is in italics after each rule.
1. Always insist that you see your tattooist remove a new needle & tube set-up from a sealed envelope immediately prior to your tattoo.
The needle is in a long thin package. The tube is to the tattoo machine as a grip is to a pen. It's the part that the artist holds onto. Sometimes the tube is steel, sometimes it is plastic and disposable. Either should come from a sealed autoclave envelope.
There are a few artists who set up before you are seated. If you know and trust them, fine. If not, ask them to open new stuff in front of you. It may seem annoying, but I'd certainly rather be an annoyance than walk out the door with hepatitis.
2. Be certain you see your tattooist pour a new ink supply into a new disposable container.
Ink should go into small, single use caps. Ink should never be reused.
3. Make sure your artist puts on a new pair of disposable gloves before setting up tubes, needles and ink supplies.
And every time he needs to touch something that is not on you or your tattoo setup he should take off those gloves, do what he needs to do, then put on a new pair when he returns to you. If he walks away from you with gloves on and comes back still wearing them, ask him to put on a new pair.
4. Satisfy yourself that the shop furnishings & tattooist are clean & orderly in appearance; much like a medical facility.
I personally think some tattoo shops are cleaner than some medical facilities. But a good rule? If you wouldn't want to eat there, don't get tattooed there. If you wouldn't trust your artist to make you a sandwich, don't trust him to tattoo you.
5. Feel free to question the tattooist as to any of his sterile procedures & isolation techniques. Take time to observe them at work & do not hesitate to inquire about their experience & qualifications in the tattoo field.
Usually their answers will be matter-of-fact. Not because they aren't interested in answering you, but because they have answered so many times. That's usually a good sign.
6. If the tattooist is qualified professional, they will have no problem complying with standards above & beyond these simple guidelines.
If he doesn't want to answer questions, run.
7. If the artist or studio does not appear up to these standards or if they become evasive when questioned, seek out a professional tattooist.
It's always better to wait if you're not sure. I've said it before, follow your gut. If any little part of you is thinking that this tattoo is not going to go well, get up and leave. Just get up and leave. It's not the end of the world, just the end of a bad tattoo.