Check out the shop thoroughly. Don't be lulled into a false sense of security by a clean look. If the needles are not disposed of after each person, then it MUST be "autoclaved." Autoclaving is a process that pressurizes the instruments and kills any virus or bacteria that might transmit viruses or bacteria. My dentist has two autoclavers--one gas and one steam--both pressurizing down to 250fsw. He also has spore samples that he autoclaves and sends to a pathology lab to make sure the machines are working. Ask the artist how they clean their needles. If they don't say they autoclave, you are taking your risks. If they say they do, ask to see their machine. Note that in some states, autoclaving is required by law. Other common-sense types of things include throwing out the ink after each customer. Make sure the artists have small wells for each ink color that they dispense from a larger container, and that these are thrown out after work on you is done. Compare the conditions of the shop to that of your dentist--does the artist wear gloves? Are the areas sprayed clean?