Thank-you notes after job interviews should be thoughtful, specific and timely. While a thank-you note (or lack thereof) is unlikely to make or break an individual's candidacy, it does contribute to the "overall picture" of a candidate for a job.
Alison Green, a hiring manager who writes the popular career advice blog Ask a Manager, recommends email thank-you notes above paper thank-you notes for their timeliness, which can be critical in a fast-tracked hiring process. She also cautions a candidate not to draft her thank-you note prior to the interview or drop off her thank-you note with the receptionist as she leaves. Doing so prevents her from referencing information from the interview, and makes the note seem less thoughtful.
A candidate should also think of her follow-up note as a way to strengthen her candidacy and express enthusiasm for the position, not just to express thanks for the interview. Green recommends that a candidate send follow-up notes within a few days after the interview, but no earlier than a few hours after the meeting. According to Green, employers want to know that the candidate thought about what was said in the interview and concluded that she is still excited about the job. However, Green states that any sort of follow-up note is better than no follow-up note at all.