Practice by preparing well for every interview, even if it isn’t for your dream job. Especially if it isn’t your dream job. If your life and happiness doesn’t depend on whether you get hired, you will be more confident asking direct questions about a company and answering tough questions about yourself. If you stutter or say something ridiculous, it won’t be the end of the world. Every conversation you have raises your comfort level when telling your own story.
A manager recently told me that he pushes people in interviews. He said he asks about each of the technical skills he sees on a resume or application. If they say the know Windows, he wants to know which programs and how someone used them. This can be intimidating, but preparation is your friend here. Recruit a buddy or mentor or just pick up the phone and call yourself and explain your work history. Answer questions you might be asked, including reasons for leaving and what your successes were. Every time you speak something out loud, you become more comfortable hearing yourself say it; you will start to hear yourself overexplaining or going off on a tangent and you can then edit yourself down to statements that are true and comfortable to say and to hear.
Job interviews and sales calls both are fairly predictable. There’s the occasional trick question or unexpected personality that you might have to deal with, but generally, when you’ve done anything more than a few times, you have a good idea about how it will go. Practice interviewing every chance you get. Stutter, stammer, talk too loudly, wear the wrong shoes and misjudge distance and time. Get it all out of the way when the consequences are low. That way, when you really have something on the line, you’ll win
Did Venus Williams play tennis before she got to Wimbledon? Did Barack Obama govern before he won his first presidential election? Was it raining when Noah built the ark?