Know your employer: You may be able to use another company's interest as leverage in your current job, but you need to know your company first. Some companies won't negotiate unless employees have another suitor. Others will have you escorted to the door if they hear you've been interviewing with a competitor. "Some truly will say: Hey, enjoy the interview, and don't forget to pull your stuff out of your office on the way out, because you've just been fired," Karsh says. "Others may say: Oh my gosh, we can't lose [her]—she's too valuable."