An old boss gave me some great advice: if you want a promotion, behave as though you’ve already got it. Don’t sit at your desk stewing about all the smart things you’d do if you got promoted. Just do them. How could you boss not give you the promotion when you’ve already proven you’re capable of the job? (While you’re busy proving yourself, make sure you’re mentoring someone to fill your old position once you officially move into your new role).
What if you want to switch departments? A media buyer thirsting for a career in client services? An account exec yearning to be an art director? This is trickier. In this case, doing the job you want before you have it will likely cause problems. Try to find a volunteer position or training course that gives you a chance to build those competencies and a portfolio. Now you have something to back up your request to switch streams. If you’ve been in your current position for a while, you may find you’ll have to change companies or even markets to escape your reputation and redefine yourself.