I recently decided to go down the same path as the OP, and this advice may not work for you but it did for me, so i thought i would put my two cents in.
Once you get past where and how large, the only thing that helped me out was to find something that describes the most basic idea from which you branch your ideals off of. To show you what i mean, the cross is a symbol by which people project the larger ideal of a god, and the way of life that falls under following that deity. I thought through many of the more serious ideas that people usually give, and it seems the more i asked others for what would express that the best, i got farther away from who i am.
I landed on "Can't Be Saved", it's the name of a song from the rock band senses fail, I've had the song since it came out, but only when i was rolling down the 101 and it came on when my ipod was on shuffle did it click to me..
It rests on the side of my arm closest to my chest on my bicep- this shows enough that those who don't care/can't understand will dismiss as just a dumb quote. It could be extremely useful in a situation where possibly "screaming" athiesm isn't the best idea- and I'm sure we all know, no matter how passionate we may feel about some things, there will not always be people ready to be tolerant of what you think is right
For me, and those intrigued enough to find out, it means that the only path that will succeed for me is one i tread alone, without the assumed help from a greater power, or anyone else for that matter. Another thing that was very important for me that it doesn't promote that I believe that path is right for everyone, but it
is who I am.
cliffnotes 
1.Find out what Atheism means to you, look in your own day to day life for what speaks that, and it doesn't hurt if it looks sick. It worked for me.
2.Or you could just get zombie jesus. Frankly I don't see enough of those.
