OP –take note of ProblemSusan's post - my experience also.
it's about the interview, forget the application
Assuming there's more than one interviewer make sure you look at each of them even when answering a question from one of them.
Looking a person in the eye is difficult so look at their eyebrows and they will think you are looking at them.
As someone said, shoulders down, such good advice, as it relaxes the chest. Tight chest = tight vocal cords = equals higher pitched voice. It's easier to relax chest if you push out your tummy a bit – no-one will notice that.
Ideally dress down – lots of bling tends to detract from what your saying.
If you've got time, practise what you want to say out loud – yes really. In the shower, in the car anywhere you can.
Walk in – move your chair ever so slightly (assertive) put handbag on the floor beside you, look up and smile.
At the end of the interview they should ask you if there's anything else you want to say – have a short sentence ready which you've practised out loud that finishes with three words that describe you.
Your reply should be along the following lines:
'I would like to say that if you appoint me I can offer you hard work, dedication and experience' and then say nothing else, nothing else – let those three words hang in the air. (you choose three words to suit you)
Long, long after you've left the room those words will stay in their minds. Honest.
The psychology behind it is sound.
Finally, females in interviewees tend to play themselves down, men the opposite.
All the best.