1. Career considerations. While many industries are becoming much more open to visible tattoos, many others will likely always expect a more conservative appearance. Think seriously about your career goals before getting a visible tattoo.
2. All skin is not the same. Bend your wrist forward - see those wrinkle-like lines that form? Tattooing over those lines is a near guarantee that your tattoo will heal and age poorly. Hands, fingers, feet, and facial skin all pose their own unique challenges as well. This isn't to say they can't be tattooed or that they won't look good, it just means you want to consider the type of skin you'll be having tattooed before making your final decision. Talk to your artist, and ask them how the location will affect the way it heals.
3. Size. In order for a tattoo to age well, it has to be an appropriate size - that is, if the design is intricate, or incorporates words or numbers, it needs to be large enough that the lines can spread a little without losing those details. This means the location you choose has to accommodate the size of the piece - larger pieces are best done on the back, as a sleeve, filling your calf, or across the chest or stomach.
4. Body changes. No matter your age, your body shape is not likely to stay static. Whether it be due to weight loss or gain, aging, a pregnancy, bodybuilding, unforeseen circumstances such as an illness, or hormonal changes, the shape and size of our bodies can change drastically over time. Keep this in mind when choosing your tattoo's location - while not all changes can be planned for, most can. Women wanting to get pregnant in the future should hold off on stomach or ribcage pieces; anyone planning to lose or gain weight should consider that before getting a currently really flabby or really bony body part tattooed; young people should keep in mind that the location they've chosen may one day sag.
5. Ink is addictive. We've all heard the old potato chip slogan applied to tattoos: betcha can't get just one. For many, this is all too true, and if you don't consider where you're going to want to put those second, third, and fourth tattoos, you may end up with a messy collage of mismatched pieces on your arm or leg. Before you get your first tattoo, think about your future plans - do you eventually want a sleeve? Then you probably shouldn't get a single, small tattoo on your arm. The same goes for any other part of your body - give a little thought to what other pieces you may want before deciding where to put this one.
Getting your first tattoo is an exciting, monumental moment. A little care, consideration, and research will ensure you are just as happy with it ten years from now as you are today.