What you think you're doing: Being polite.
Why it doesn't work: Rosemary Haefner, VP of human resources at CareerBuilder.com, says candidates often agonize over the handwritten versus email thank-you quandary, and then shoot off a generic letter of appreciation. But getting the form right is less important than taking advantage of your last opportunity to connect with the interviewer and show why you're right for the job.
What to do instead: Haefner says a general rule of thumb is to send an email within 24 hours, thanking the interviewer and mentioning specific points that came up in the interview. Some career experts say a handwritten note is a nice touch, but choose your stationery carefully: That glued-on glitter looks a lot less nice when it winds up all over someone's desk.