Reading by far ! I just had to pick up a mountain of books I've read to donate to the library. I have a couple of sheets of paper on my desk for months with the few things I've written.
You don't "become" an atheist. You weigh all the options, read the Bible a few times, decide if you have faith in the unknown or believe in concrete scientific evidence.
LOL! It's not like you have to sign papers or graduate from atheist school. Just worship the Flying Spaghetti Monster!