To make a will you must be of sound mind and at least 18 years old.
You will need to choose an Executor, a person you trust enough to manage your estate during the period of administration, after your death. The job of an executor is not a simple one and you will need to speak to the person you are appointing before you choose them.
A will does not become final until your death and so long as you are mentally competent you can change your will at any time.
Periodic reviews make good sense.
Life can be unpredictable and each particular individual situation may include births, deaths, marriages, the dissolution of marriage, new tax laws, the purchase of something, the sale of something. A subsequent marriage may ‘blend’ families. Your death may leave minor children or persons with a disability to be cared for. Other complexities may include separation agreements, investment portfolios, trusts, joint ownership, digital assets, private corporations, rental properties, gun ownership… to name but a few subjects.