I thought I'd write a post about the way I see my beliefs, and how evidence (whether for or against) interacts with my beliefs. This post is just about my personal views, and I'm not speaking for anyone else here.
I'll start with the big question of god(s). I don't believe in any deities, you probably already knew this though. What many people don't seem to understand, is that disbelief is not a claim of having all knowledge. When it comes to the issue of belief in god, there are two separate axis, lets say the X axis is belief, and the Y axis is knowledge. On the far left of the X axis is Theism, on the far right is Atheism. Agnosticism is not a statement of belief, but a statement of knowledge. Agnostic is literally 'a'-'gnostic', where 'a' is the negative prefix and gnostic means possessing knowledge. So our Y axis is knowledge, with Gnosticism being on the top of the axis and Agnosticism being on the bottom. This is important to realise because Agnosticism is not some sort of 'middle ground' between Atheism and Theism, it's on an entirely separate axis.
I would place myself on the far bottom-right corner. Meaning that I do not believe in god(s) and I have no knowledge pertaining to god(s). This is where evidence comes in to play. There is no positive or negative evidence concerning deities. We have nothing that confirms or denies the existence of gods. The default position (or rational position) on a subject where there is neither positive or negative evidence is non-belief and I'll explain why.
If someone made an outlandish claim, that little green men are dragging the earth around the sun with a rocket-powered go-kart would you believe them? Most certainly not, as there is no supporting evidence. However we do have evidence concerning the actual causes of the phenomena that the outlandish claim was purporting to explain. We DO know why the earth orbits the sun.
This situation is very much like the situation with belief in gods, and in religion. For example, the Bible says that God created the earth in 6 days, and then has a genealogy from the first man all the way until Jesus (though the genealogies are contradictory and incomplete) which is where people get the idea that the earth is 6000 years old from. Whether or not you believe this story to be literal or not is besides the point because for years and years, it has been the status-quo among believers. Although we may not have evidence concerning the existence of god itself, we do have evidence concerning the biblical creation account. We DO know how old the earth is, we DO know where humans came from and we DO know what causes the phenomena attributed to god in the creation account.
So while we may not be able to prove or disprove the existence of gods, we can certainly determine the truthfulness of claims about the nature of god, the universe and everything. This is the main method of reasoning that caused me to become an atheist. I refuse to believe extraordinary claims without extraordinary evidence.
EDIT: Here is the graph I mentioned at the beginning