But assuming you have got one... or a "friend" has...
It depends on tattoo size as to which treatment can be used e.g. laser (or surgical etc).
Also, certain inks formerly responded poorly to laser removal i.e. black ink. Just, as tattoo removal on black skin was less successful with those lasers. It was because the laser latched onto the darker pigment and tried hard to remove it burning the skin.
Painfully.
Some newer, more sophisticated lasers apparently don't have this problem.
That's just some very basic info so might help as a starting point for you to look into it more. I don't know too much about it beyond that though. If I get time I may try to search for some further info though.