In addition to the above excellent advice:
Brush up on some common psych conditions and medications...no, you don't need to know them all in detail, but just the basics.
Know the serious adverse effects/syndromes of medication (e.g., EPS: tremors, involuntary tics, rigidity; NMS: high fever; SJS: rash; note that this is not a complete list of either effects or syndromes) and how you would treat them (stop the med, notify MD, administer anticholinergic or other medication; again, not a complete list of what to do for what. Giving you some homework to do
Remember that psych patients, even involuntary ones
, have the same rights as a medical patient. That does include the right to refuse treatment and medications (unless they are court-ordered).
Also remember that patient safety is ALWAYS the priority...and can trump patient rights if it has to. If you're presented with a scenario, choose the response that puts safety first.
And if you don't know the answer to something, don't try to fake it because guessing wrong will make you look worse. State that you don't know know the answer but that you would find out from a coworker, supervisor, reference manual, etc.
Good luck with your interview!