WHEN I first started as a freelance writer, I was eager to sell myself — but not eager to have to discuss money. So I more or less took whatever was offered. Then I read somewhere that no matter what price a new client states, you always say in a polite but firm tone, “I expected more.” The first time I tried it, I was sweating and I doubt my tone was firm — it probably sounded more like pleading — but to my great surprise, it worked. With that one sentence, I made an extra few hundred dollars. Negotiating a salary when you have a job can be...