Characteristics of a valid will

Ambulatory: a will is said to be ambulatory in that it only speaks after death. It distributes a persons property in death.
Revocability: a will is revocable by the test or at any time when he has capacity to make it.
Capacity: for a will to be legally valid the testator must have had the requisite capacity. Thus, not every person can make a will.
Formalities: the validity of an oral or written will is dependent upon compliance with the formalities prescribed by law.