Although many people understand that post-interview follow up is an essential part of interview success, few ever put it into practice. Which is all the more reason for you to do so.
Interviews rarely end on a handshake and a job offer. Usually an employer will spend some time deciding who the best job candidate is. It's during this crucial decision-making period that your actions could help swing things in your favor.
Send a thank-you letter within twenty-four hours to the attention of the person who interviewed you, and express your gratitude for their time and consideration. This kind of prompt follow up helps keep you in the employer's mind. The letter doesn't have to be poetic, but some effort should be exerted to maximize its impact. Reiterate your enthusiasm about working for the company, and make a final “closing argument” about your qualifications for the job and what you hope to bring to the company.