I am an independent consultant, and most of the work I do is related to HR (human resources) systems, which means I work with a LOT of HR folks. Over and above questions others have asked above (are you going to like it 40 years from now, etc.), is whether it will impact your career choices in the future. Note that I am not against tattoos in general - if you really want one and can say it works for you now and in the long run, I say go for it, from a personal perspective. But from an HR perspective, you should consider:
- Have you yet identified what your future career will likely be yet?
- Are tattoos common among people in that field?
- Is the technology in that field changing? If so, if that field becomes obsolete in the future, what is your "backup field" to switch to? You need to ask these same questions about your backup field.
- Consider there used to be no Internet; no one had an idea such drastic changes would be coming. What if some huge technological breakthrough occurs that makes both your primary career goal and your backup career goal obsolete?
- Is the size/shape/placement of the tattoo such that you could cover it with clothing if your career depended upon it? If so, consider environmental factors: no one wants to wear long sleeves in the middle of summer in Southern U.S.
- If tattoos are acceptable in your initial career goal, are they acceptable through the chain of command? In other words, if you go from having a "line" job in which tattoos are acceptable to a management job where they are not, are you possibly limiting your future career advancement?
If you can say to yourself "I'm going to become an aircraft mechanic and many people in that field have visible tattoos, and while technological changes in that field will occur, it is most likely that through the course of my career having tattoos won't be a problem", then it's unlikely that getting something easily visible would be a problem. There are professional careers (most notably in creative fields such as graphic design) in which tattoos are simply considered to be individual expressions of creativity, and no one cares. But if you are going to work, say, in the finance department of a company (finance tending to be a very conservative career), then you should probably consider getting something that is easily covered. Even if you are going to work for yourself, such as I do, what kinds of attitudes might your potential customers have about tattoos, and are you willing to accept that you will lose out on business opportunities if you have visible tattoos? The fact is that some people make faulty assumptions about people with visible tattoos, such as they assume people with tattoos are drunkards or druggies. Can't get away from that, unfortunately. So if you're going to go with something that is hard to hide, understand that this is something you need to learn to deal with, and getting angry is not a productive response.
So yes, consider it carefully, not just in light of your current desire, but also in light of your desired career options. Again, some careers are fully open to people with tattoos, all the way from the janitor to the president, while others are even downright closed. Don't be afraid to call some people or even HR departments of companies that have your desired career field, and ask how they feel about them. Don't take just one response, though, get several.