How would you go about taking someone's life?

Now, this is a kind of weird topic, but I'm curious. I have always wondered how normal people end up in these situations and how they deal with it or even get away with it. Some really in-depth "fantasizer" might be able to answer my question or anyone, give me your input. How would you go about killing someone and then getting away with it?

must have a character, be helpful, not gossip .. in short it should be honest