You should listen, more than speak. Don't belittle the patient's sickness. The patient my complain about the medical treatment they are receiving, don't undermine the staff's authority or expertise. You want to encourage the patients, so don't bring bad news about the world. The patient may want, however, to talk about the news.
Men often enjoy talking about their work.
Women often enjoy talking about their family. But don't argue or theologize. Don't carry a large Bible. Accept any interruptions of your visit from doctors, staff, or family. Often there will be opportunities to visit and minister to the family.