Actually, most tattoo shops work with you to create a design. While there's certainly cases where you show an artist what you want to have done or you pick out of a catalog, being friends with people in the industry really opened my eyes to the world they live in. Tattoo artists are just that, artists. My kraken, for instance, is entirely original. I told my friend who owns a shop in Edmonton I wanted to get a kraken done, and he came back to me a few days later with a text message showing me the line work for it that he drew by hand. They work with you to get something you want and would be proud of, and it's their reputation on the line; they want their piece to be something they're proud of, as well. Your new tattoo is a part of their legacy and portfolio, and their reputation is on the line if it's something that's done badly. It's the reason most tattoo shops refuse to do hand, neck, and face tattoos, which are known as "career killers" among a lot of artists, unless the client has most of their body tattooed already. It reflects badly on them if somebody can't get a job or deal with the social stigma of having visible tattoos.
So, with that in mind, if you are interested in getting a tattoo and have a general idea what you want, find a reputable shop and check out their web page or Facebook page and see what kind of work they do and what artist has a style you like, and let them know what you're interested in. They'll probably do the same thing for you as they did for me and they won't start the actual ink job until you're satisfied with the design.
The thing I hear a lot from people is they don't want to get a tattoo and realize down the road they hate it. The only time I've ever heard anyone with a tattoo regretting what they got is when they made a stupid half-assed decision and got a really ugly cheap tattoo done. Case in point, look at the poll. Everyone who has a tattoo is happy with what they have, and almost everyone else is thinking about it. Chances are, whatever you get done will be something you'll love for the rest of your life. Like I touched on before, it's kind of a portrait into the time of your life when you had it done, and it's got a story to tell. That to me is pretty awesome, and honestly, I find tattoos to be such a great conversation starter that it really helps with something like social anxiety. I have had a lot easier time starting conversations with strangers with tattoos than I did before hand.
Anyways, sorry, that was kind of more of a general post for anybody who's on the fence about it, but I wanted to address the "what if I make a mistake?" mentality.