One of the most common question asked is "You are at the end of your shift and the relief staff has not arrived. What do you do in this situation?" - The best answer is to tell them that you would not leave your station until properly relieved by an approved staff, and that you would call the appropriate person to inform them of the situation so that a substitute could be found. Also to ask if it would be appropriate to start calling "fill-in" staff on the employee roster to find a replacement. This lets them know that you will act responsibly when a situation arises like that.
Other common questions asked are variations on the potential employee's knowledge of the Vulnerable Adult Law, and the proper procedure for reporting suspected violations. I would read up on that one before the interview.
And also, dress professionally and pause before giving each answer. It does give a good impression to the hiring person that you are giving some thought to your answer. When asked if you have any questions, this is the time to do so. Ask what your typical work duties would be like, and also what sort of challenges are you likely to face if chosen. Make sure you DO NOT ask questions that have the answers available on the companie's website or in the information given you already.
I'm sure there are many other tips, but these stood out for me.