Legal background to trusts and estates: a valid will
A will reflects the wishes of the person making it (a testator). It explains how to dispose of his possessions (estate). The testator must acknowledge, in the document, that it is his will. He has to sign it in the presence of two witnesses. The witnesses have then to sign the document in his presence, and normally in the presence of each other. The document (often called the last will and testament) has to follow the correct format.
A testator can alter a will without scrapping it, by preparing a codicil. This is a separate document that alters or explains the original. The testator must sign it in the presence of two witnesses. They must then sign it in the presence of the testator. They do not have to be the same people who witnessed the original will.