Most people say that body art will sting based on the spot where it is located. Spots that are surrounded by a lot of fat are usually much less painful. For instance, tattoos on the backside are usually not as painful to get. Having it done over somewhere where there is a lot of bone near the surface is the worst place to have it done, or sensitive areas.
If you are worried about it hurting then two locations you can trust are the upper arm and the bottom of the leg, getting them in these locations should minimise any discomfort.
Getting a tattoo will hurt if you don't take good care of the tattoo at first. In a sense, the tattoo is a wound. It has to heal properly and that will not happen if you don't cleanse and treat it. You must keep a close eye on your tattoo if you want to prevent infections and complications.
Check with your artist about how best to look after your new tattoo, they usually have special wax that works wonders for it. If you do not keep your tattoo moisturised then it can form scabs, which if knocked off will take bits of your tattoo with them.
You may do everything right though and still get an infection, this would be the artists fault in that case. Getting a tattoo splits the skin and makes it open to infection, so if the parlor is not clean, or heaven forbid, they reuse needles, then you stand the chance of picking up and infection. The only way to prevent this is to scope out the place before you commit to anything. Try and ask if you can watch someone else first. That way you get to see if they are using fresh needles and taking good care before you put yourself in the hotseat.
Some tattoos become tainted due to an allergic effect to the color. So before you obtain your tattoo, talk to your doctor about how you can figure out if you have allergies to the elements in most tattoo ink.
So in conclusion then having a tattoo is not really that painful, as long as you follow my advice and have it done in a reasonable area with some fat or muscle to protect you and take some basic precautions with who you use. If you do all that then you should have a very good experience.