There are only a couple of requirements to make a will valid and legal.
Soundness of mind: The person signing the will cannot be mentally ill or disabled and must be acting of his or her own free will, without undue influence from others.
Witnesses: At least two people (three in some states) must watch you sign the will. They cannot be related to you and cannot be entitled to receive anything under the will.
In addition, a will's appearance must be uniform. This means all important sections must be entirely typewritten, computer generated or handwritten. You do not have to get your will notarized.
However, LegalZoom allows you to "self-prove" the will, which requires that a separate affidavit be notarized. The advantage of self-proving for most states is that witnesses do not have to be tracked down to verify the validity of your will after your death.