It depends on the patient.  I have found with head injury and bipolar patients, a lack of eye contact is a must when their individual 'moods' are on them.  Sometimes not looking them in the eye and keeping up a stream of chatter (or none) lets me do what I have to do with them without me receiving a beat down.

Alzheimer's can most of the time be redirected.  With these patients I try to pick up the thread of their conversation and talk away as if I know what they're talking about.  I also use tons of hand signals to let a patient know what I'm about to do.  I will tug on my pants while I say, "I've got to change your underpants!"

Singing songs from that person's era can be especially helpful, or religous hymns of their liking.

Sometimes, they just want you to listen to them get their frustrations off their chests.  Some "mmm-hmm's" and open-ended questions work well.

Reminding the patient that "The doctor ordered this.......", "I'm sorry, I"m just trying to do my job/take care of you/what the nurse asked me to do for you........."  "I'm here for you, if you want to talk about anything......"

Saying things like, "How about if we get your nightgown on, then I'll get you an ice cream?" sometimes works.  Putting yourself in their position helps, too.

I also find it makes patients feel good if they can help you in SOME way.  "Hey Mrs. Jones, can you remind me at 8:00 to..........*whatever*"?

Listen to the patient............I've put the biggest smiles on their faces by picking up things like, "I wish I had enough money for a Coke" and then appearing with an icy cold one for them, or cooking something at home and bringing in some for them.  It's crazy what the simplest food item can do for their spirits.