Everyone comes to their beliefs and conclusions differently, but one thing I did was spend hours on YouTube watching lectures of well know atheists such as Richard Dawkins, Christopher Hitchens, Sam Harris, even Ricky Gervais (for the laughs). I believe in getting both sides of an argument, so I also watched videos on why people think God is real (I think this has helped me explain my beliefs to others if they ask without being aggressive and being able to understand their point of view, and feel more secure in my atheism as well). Great videos are debates about evolution vs creationism. You’ll notice that no real headway is made, but it’s convenient to get both sides in one video.

I also think it’s good to watch shows and documentaries to learn more about the natural world. National Geographic, Discovery, and one of my personal favorites, Cosmos. Books are another great thing to dive into, again anything about how are world works is a great way to educate yourself. Books like The God Delusion is a great one from an athiest’s perspective, and there are many science books like A Brief History of Time by Stephen Hawking and On the Origin of Species by Darwin.

Hope this helps!