Full answer
A last will and testament has four core elements in most US states: a declaration that this is your will, the appointment of an executor (the person who carries out your wishes), specific bequests of assets, and designation of guardians for any minor children.
For a simple estate, online services like Trust & Will, LegalZoom, or Nolo provide state-specific templates for $30–$200. These are adequate for straightforward situations with no business interests, blended families, or large estates.
To make a will legally binding: write or type the document, sign it in front of two witnesses who are not beneficiaries, have both witnesses sign in your presence, and store the original in a fireproof location with your executor knowing where to find it.
A holographic will — entirely handwritten and signed by you — is valid in about 25 states without witnesses, but it is more susceptible to challenges. Complex estates, significant assets, or blended families warrant working with an estate attorney. This is general information, not legal advice.