I think! Dress well, no jeans, t-shirts, etc.
Do some research about the store?
The person you interview with will probably ask if you have any questions. You should prepare some in advance so you just don't gesticulation your shoulders.
Impress the BOSS, and most of the above doesn't make any difference...
Not all bosses are easily impressed and not all people have enough to impress. In that case, all above makes sense. Most important thing to do is be yourself. If you 'polish up' your credentials or capabilities, you will fail in the end.