A few years ago, my book club read a book on being transgressive in the workplace. It wasn't a particularly wonderful or memorable book, but there was one sentence in one chapter that has become a guiding principle for me: Everyone should have their own personal board of directors.

Since then, I've intentionally collected mentors whom (whether they know it or not) I consider to be members of my board.

Here's why your board is a critical part of your career development, and three tips to build you board.