Alzheimer's Society UK offers a very useful guide called Taking part: activities for people with dementia. Chapters cover conversation, creative arts, members of the community and more. Can be purchased for £30 (abour $45) from the online shop.
What to Say
Avoid asking too many direct questions. People with dementia can become frustrated if they can't find the answer. Ask questions one at a time, and phrase them in a way that allows for a 'yes' or 'no' answer.
Try not to ask the person to make complicated decisions. Giving someone a choice is important where they can cope with it, but too many options can be confusing and frustrating.
If the person doesn't understand what you are saying, try to get the message across in a different way rather than simply repeating the same thing. You could try breaking down complex explanations into smaller parts and perhaps also use written words or objects.
If the person says something you know to be incorrect, find ways of steering the conversation around the subject rather than contradicting them directly. Try to figure out the feelings they are sharing.
Listen carefully to what the person is saying, and give them plenty of encouragement.
When you haven't understood fully, tell the person what you have understood and check with them to see if you are right.
If the person has difficulty finding the right word or finishing a sentence, ask them to explain it in a different way. Listen out for clues. Also pay attention to their body language. The expression on their face and the way they hold themselves and move about can give you clear signals about how they are feeling.
If the person is feeling sad, let them express their feelings without trying to 'jolly them along'. Sometimes the best thing to do is to just listen, and show that you care.
Due to memory loss, some people won't remember things such as their medical history, family and friends. You will need to use your judgement and act appropriately around what they've said. For example, they might say that they have just eaten when you know they haven't.
Body language and physical contact
A person with dementia will read your body language. Sudden movements or a tense facial expression may cause upset or distress, and can make communication more difficult.
Make sure that your body language and facial expression match what you are saying.
Never stand too close or stand over someone to communicate: it can feel intimidating. Instead, respect the person's personal space and drop below their eye level. This will help the person to feel more in control of the situation.
Don't underestimate the reassurance you can give by holding or patting the person's hand or putting your arm around them, if it feels right.