Getting selected for an interview was your first hurdle. You cleared that! Now it's the interview. If you prepare for this you will improve your chances of success immeasurably. Here are some tips:
After the Interview
Follow up with a letter
Hardly anyone does, and this gives you an opportunity to stand out from the crowd. Say how much you enjoyed talking with....... And that you are looking forward to hearing from him/her.
Think about the questions you were asked
How could you have answered better? Did you bring in all your relevant experience? Overall, what went well and what could you improve?