You're trying your best to make people laugh; then if you fail, they hate you. But your intent's the same. It's not like you're trying to do evil to them.
I sort of try to write everything for me. I'm a huge sports fan but have no interest in minutiae. I don't remember who won Super Bowls five years ago or listen to sports talk radio. I'm trying to make sure the jokes are self-contained so they're accessible to everyone.
I generally have a real strong idea or a strong punchline, and I just try to get to it by rambling around, as I don't like to memorize words.
On Update, the only real original thing was trying to take away the cleverness of the punchline and make it as blunt as possible.