As long as you get tattooed in a safe, health assessed studio by tattooists who know what there doing with regards to health and safety (usually they will have a health assessment document stating that all sterilising equipment works correctly, needles and clinical waste are removed from site safely etc) then you have absolutely nothing to worry about.
Most, if not all, tattooists will usually open pre-sterilised Etheline oxide treated needles in front of you so that you can ensure they are using clean equipment.
Grips (if not pre-sterile disposable plastic e-o gas treated) will have been sterilised in a hospital standard autoclave to ensure all bacteria that can cause harm to you (AIDS MR-SA HEPB etc) will have been killed off. These are usually stored a an sterile autoclave bag and again opened in front of you to ensure you know the equipment is sterile.
If you are worried ask to see the autoclave (looks like a big microwave) which is usually kept in a separate room to that in which the artists work to ensure cleanliness.
Things you can look out for going into a studio should be
Licences of all artists working in the studio in full view of the customers which are given by the local health authority or district council. these must be in full view of customers either in a workroom or in the main waiting room by law.
Overall cleanliness of the studio. General rule of thumb, if the shop looks messy, then so are the artists. Most respectable studios will be presented as clean, sterile environments.
Make sure that the artists are cleaning all stations, using new needles/grips/disposable workstations and water cups between tattoos.
Most tattoo studios are actually cleaner than some hospitals and there are no proven registered cases (that i know of) of a licenced studio giving anyone AIDS/MR-SA or HEPB. This is mostly due to tattoo studios being health assessed roughly every 6 months/yearly to ensure all health equipment works correctly and general standards meet those outlined by the local health authority
Tattooist 3 years