After you've attended a job interview, sending a brief interview follow up letter or (follow up email if appropriate) is a great idea.

Not only does it show the company you are interested in the position and are a professional person, it can help to keep you top of mind in the eyes of the hiring manager who may have interviewed many people for the position.

Just make sure you keep the letter/email brief and ensure that there are no spelling or grammatical errors. You don't want your good effort to be wasted if it contains typos that makes it look like you can't write properly.

Also, make sure you send the interview follow up letter in a timely fashion ie. on the day of the interview or the morning after at the latest. No point in waiting longer than this to send it.

Once you've sent a thank you letter after the interview, you might just want to wait to see how things play out rather than sending another note if you don't hear anything back.

It can sometimes take awhile for a company to actually wrap up a job search for a new staff member so any delay might be for unavoidable reasons that you're not aware of.

I understand that you're probably excited about the possibility of getting the job and you want to hear back from the company as soon as possible.

Hopefully the company gave you an indication of their timetable for hiring someone or at least gave you an indication of when you should

If you haven't heard from them by the date they suggested they'd contact you, you might wait for several days and then call or email your contact at the company just to see what is happening next.