I used to be a stickler about handwritten thank-you notes. And if you're going that route, get classic flat note cards with your name or initials engraved on them. No foldover cards. No flowers or butterflies. Simple and sophisticated. That said, I've softened my stance on the handwritten note and think it's fine to email a thank-you. In fact, if you know the clock is ticking toward a decision or it's a digital job, email is the first line of defense. The crucial point, though, is that your thank-you has to specifically mention something you talked about in your meeting, and it has to be thoughtful—and short. Five sentences MAX. Or it's TL;DR. Simply thanking your interviewer for her time is a waste of her time.
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You have to say something that makes you stand out from the crowd. The most nerve-racking part of the proper follow-up protocol is how to follow up again if you don't hear back. The truth is that people are phenomenally busy and email can easily get lost in the shuffle. If you don't hear back in 2 weeks, email again reiterating how excited you'd be to join an organization that's doing such amazing things. If you still don't hear back, some people say a third email another 2 weeks later is okay. I think it's just like a dude who doesn't return your text or your smiley face reminder: He's moved on and so should you.