Your Will must be signed by you in the company of two adult witnesses.  The witnesses sign indicating that they can verify your identity and mental capacity to create a will.  These witnesses should preferably not be beneficiaries or Executors of your estate.  They must also be present in the room at the time you sign the Will.
Though you may want to include burial instructions, it’s best to leave these out since your loved ones will need to make decisions promptly upon your death — they may not have time to look to your Will.