An attested will is a will which has a witness that signs as a witness present. The witness will generally attest to the fact that a certain individual wrote the will and that they were of sound body and mind when they did so.
Each jurisdiction will have specific requirements for an attested will. For example, an attested will must be in writing in most jurisdictions and the will should have at least two witnesses whom are not named in the will.
The attested will must also be signed by the individual writing the will, as well as dated. Anytime the will is changed, the signature and date must again be noted. When the will is originally written, the witnesses will also sign and date the will. Witnesses would again be present when changes are made to the will, although it does not necessarily have to be the same witnesses.
Each state has various requirements about signatures on an attested will. For example, the person writing the will may simply use initials or their last name as a signature. In addition, most states require that the witnesses sign at the same times as the person writing the will signed, but this is not always the case.
While there are some specific laws which apply to writing a will, there are also issues which are simply good practice. For example, it is advised that the writing of the attested will be witnessed and video taped, in case there is ever a questions as to the writer of the will, or their state of mind.