I guess you probably heard in manga animation or if you practise martial arts the word ki Ki means spirit, energy, what flows. Its a very common kanji in japanese and you mainly see it used as a compound.
You can find it in words like :
: ten ki : weather
: den ki: electricity : byou ki: illness
: ki bun: feelings : gen ki: healthy
You are likely to find the kanji ki written with some more strokes. As the years go by, kanjis tend to be simpler but some words or places try to keep them as their were. You will find it sometimes this way for example in the word REIKI.
Yesterday, I met with some friends who also speak japanese and we talked about the "kanji tatooing" subject. When I got home I found this page since it is not a new topic. It is well explained and shows a lot of images.
There is a blog with some drawing you can visit too. But the important thing is to be sure you want to get a tattoo with the meaning you think. Remember: a point, brush strokes and directions of strokes ARE important too and are the esence of the kanji so whats best is to take a copy of what you want. When you are sure what u are getting, just enjoy it.
I was reading my last post (in fact I made it some time ago) and came to my mind one day I was walking near a place where you can get a tattoo and I read through the designs and I was surprised that a lot where set as "japanese characters" and the truth is that they didnt mean a thing.
A girl I met last week so happily showed me a lovely design on her nake that looked quite the same as the following drawing.
I remember learning japanese and my sensei usually used to show me some of these videos and you could think "thats stupid". But in a way japanese people are quite innocent and easily laugh at these things :)