Be certain to send a hand-written note thanking them for the interview.
Also add a few reasons you forgot to mention at the interview why you would be the absolute best person for the job.
If you don't send the hand-written note with a regular postage stamp, they may not think you want the job.
Note card can be quite plain and inexpensive. Get one from your mum or a friend if you don't want to buy a box.
Good luck!!!