Things that can be written to a person who is dying include well wishes, a simple greeting, a sympathetic word or a basic account of all of the happy things that are happening around them. What is written to a person who is dying is dependent on how that person feels and how close they are to the writer.
One things that writers should always be sure of when they are writing to a person who is dying is that they have an understanding of the mental state of the person dying. If the person is feeling melancholy and does not want visitors or others to see them, it is sometimes best to simply not write them at all. If the person is in good spirits, it would be a wise idea to write them a lighthearted and fun message. If it is the person's birthday, avoid using the word happy in the greeting card. A message such as "I hope you have a wonderful birthday," may be received better by the person who is dying. Writers should always be sure to talk to someone who is very close with the dying person before writing to them to find out what type of mood and spirits they are in.