The other thing I’d ask is whether this symbol is something you think you will want on your body in 20 years.
@Fyrius is dead on: before you put anything on your body permanently, you need to understand the meaning. The yin and yang symbol is cool from a graphic-design point of view, but it also has a long tradition of meaning and symbology, and if you just ignore that, you’re probably going to regret that tattoo, probably sooner rather than later.
I mean, to take your example of the star behind the ear. That was a symbol of lesbianism in the bad old days, because when women were wearing their hair long, it was not visible, but if they went out to a place where the symbol would be recognized, they could pull their hair back or put it up in a bun so that the symbol could be seen. It’s still a meaningful symbol today, although it’s much easier to be out—but still, you were considering putting it on your body permanently, but without knowing what it meant.
Also, I don’t understand the craze for Chinese characters. Why would you want something on your body that you can’t read? How do you have any assurance that the tattoo artist isn’t going to tattoo the characters for “older whore” and “younger slut” instead of “older sister” and “younger sister”? Or that the tattoo artist even knows what the characters should be, and isn’t going to tattoo “translation error” on both of you?