Sorry this isn't all necessarily in order but a large part of my job is preparing people for interviews.
Definitely STAR.. go through your answers with someone who will be will be honest with feedback (someone who knows the STAR technique) . Spend most of your answers speaking about the A (the action that you took) and don't forget the R (so many people do)
As another poster said .. the questions you ask say as much about you as how you answer the questions.
2 questions I always advise people to ask:
What do you think my biggest challenge would be in this role?
What do you (or employees) like about working here.
Ask them a wider business question Ie 'how is the business dealing with the current challenge of X '
Always look up your interviewer(s) on linked in - it's expected and to ask them about themselves (ie how did you find the transition into this business from your previous one)
Go through the job spec line by line and think about how you can demonstrate your competency in each one. For anything you haven't done or are less strong in then get across 'I have some / limited experience in x but I'm really keen to do more of x , one of the reasons I am interested in this role / keen to move on.
Make your reasons why you are interested in the company specific ie - something that you have learnt about the company from your research Ie awards they have won, their values (always know their values) or something else from the press or their website that you have seen.
Enthusiasm and energy go such a long way. You can teach the right person to do anything but you can't teach the wrong person.
Be positive about your current / previous employer when asked before you go on to say why you are looking to leave.
Good luck !