How to get promoted: Ideal world: "I will get a promotion, then start doing the new job." Reality: "I've been doing this job. This promotion is basically a new title that reflects my responsibilities."

Most promotions happen because you've proven you can be trusted to do (at least part of) the new job. The caveat is this only works with organizations who value your contributions. Definitely don't toil away for years without being recognized and compensated for your work.