'My job offer negotiation skills are solid (I think) ... so why didn't I get anything I asked for?: Easy guide for people with 5+ years of professional work experience to evaluate and negotiate the details of a job offer

You successfully answered the questions in a phone interview, a live interview (or several) and the company just called to make you a job offer! Receiving an offer is exciting - so how do you evaluate if it's a 'good' offer? What are the important parts of an offer to understand? Are there some parts that can be negotiated, and how do you have those conversations? How can you reject an offer effectively? What contact is appropriate with other companies you have been interviewing with when y...