For knowledge, I first try to contextualize the piece of thinking into a human framework. Once I did this, I ask myself if the piece of thinking can be known by any system that can be replicated. If this is the case, then I look into it, to get a grasp of how the piece of thinking became a piece of information and the context in which it was tested. Then I adopt it, trying to remember that context.
A belief I just decide it is true. I have personal rules for it too. 1) Overall, I'd like it to be a part of my life because it makes me feel better than not having it, and 2) it doesn't hurt anyone else, as far as I know.
Obviously, off the top of my head.