How do we know what we know? What evidence do you have to support your claim?

We know what we know from what we are taught and what we learn from our personal experiences in life. Growing up, we are taught much by our parents - through watching their behaviors, interacting with them, hearing their "words of wisdom", etc. We are also taught by our teachers and peers, as well as random people in the community. We learn facts and general knowledge, cause and effect, patterns of life, and more from peoples' verbal instruction, the media... I have the evidence of my personal life as well as my friends' and my parents, and pretty much everyone I know. It's impossible to go through life without learning from other people and thus knowing the things you learn. For example, I was taught by both parents and teachers that 2+2=4. Now I know that, no question about it.
Personal experiences are much the same. We find out things for ourselves in life, and then, we know them. When I spilled hot coffee all down myself as a 6 yr old, it really hurt, and I learned that thats not a safe, good idea and to be more careful.
If you are asking the question how are we sure that we KNOW something, rather than how did we come to know things (learning) , I would say that knowledge is something you can remember over and over again, something you can use in life and something that will affect how you think and act. If you don't actually KNOW something, you obviously won't talk about it, use it to make decisions... And when life's various tests arise to test our knowledge, it will be obvious what we do and don't know. With my 2+2=4 example, if I am given a math test and I can't answer that problem, it is obvious that I don't know it. Or if I don't know that when a person gives you a hug, they usually want some sort of return action- a respnse, and giving back of affection- and someone hugs me and I just stand there, it is quite obviously I am unaware of that social behavior rule.