Having worked in investment banking (a job where your only true value add is your network and ability to negotiate) I would like to say two things:

1. I second everything in the article.

2. You would be surprised to learn how important rule #7 is. We would build entire presentations that we would provide to the other side of the table in negotiations just to reinforce our points. Basically putting ourselves in the position of “hey we’re on your side, but look at the numbers; our hands are tied!”. Having a non-confrontational attitude and providing specific reasons for why you are asking for things makes a big difference in negotiations.

(Definitely don’t need to be building presentations for potential employers though… unless it’s for contracts large enough that you’d need a lawyer and wouldn’t need OP’s advice anyways!)