Any adult of sound mind is entitled to make a will. Beyond that, there are just a few technical requirements a will must fulfill:
You don't have to have your will notarized. In many states, though, if you and your witnesses sign an affidavit (sworn statement) before a notary public, you can help simplify the court procedures required to prove the validity of the will after you die.
You do not have to record or file your will with any government agency, although it can be recorded or filed in a few states. Just keep your will in a safe, accessible place and be sure the person in charge of winding up your affairs (your executor) knows where it is.
A lawyer does not have to write a will, and most people do not need a lawyer's help to make a basic will -- one that leaves a home, investments, and personal items to your loved ones, and, if you have young children, that names a guardian to take care of them. Creating a basic will rarely involves complicated legal rules, and most people can create their own will with the aid of a good software program or book. But if you have questions that aren't answered by the resource you're relying on, or your situation is unusual, it may be worth it to see a good lawyer. For more information, see Nolo's article Making a Will: Are Lawyers Optional?