How do I personally choose which bits seem right? Was that to me headinhands? If so, I use my common sense. I use what I know of God from my experience of God in my life over the last 32 years and my understanding of the culture the Bible was written in (which is limited but not totally absent) and of my own culture.
I try and take from any bit of the Bible what I think is relevant for me.
Plus the internet is a great place to look!
Barnes' Notes on Matthew 15:3
But he answered ... - They accused him of violating their traditions, as though they were obligatory.
"In his answer he implied that his disciples were not bound to obey their traditions - they were invented by human beings. He said, also, that those traditions could not be binding, as they violated the commandments of God. He proceeded to specify a case in which their tradition made void one of the plain laws of God; and if that was their character, then they could not blame him for not regarding them."
I don't think he meant, go and kill your parents. When he was before the woman caught in adultery where the law said she could/should be stoned, he did not. So I don't take those laws to be binding on anyone. Where they came from is anyone's guess but for me they did not come from a God who loved me enough to go to the cross for me.
And yes, I hate housework too! 
PS I am off tomorrow for a few days with family so if I do not reply, please do not think I am ignoring you, I am away from the interweb! 