The biggest piece of advice I can give you is to learn everything you can about the firm and it's partners. If you know for what attorney the position is, find out everything you can about him/her. Martindale Hubbel is an excellent reference for attorney bios if their website is scant on information. Be confident about your skills, but not cocky. And don't exaggerate your experience, be honest about what you know and what you don't.
As far as salary, not knowing what part of the country you are in and what your experience is, it is impossible to predict. Good luck to you.