You have many options for writing down your wishes and plans. If you like, you can write a simple letter to your executor and other loved ones that spells out the details of your final arrangements.
Whatever method you choose, be certain to talk to your loved ones about your plans. If you write down what you want, let them know where the information is stored and how to get to it when the time comes.
Finally, it's a good idea to review your plans every year or two to be sure they still reflect your wishes. Update your letter or other instructions if you change any of the details of your arrangements.
If you need help organizing your thoughts, Nolo offers two resources that can help: