The most basic estate planning tool is a Last Will and Testament.
Everybody has a will. You either prepare your own will or one has been written for you by your state legislature (this is called the intestate law, and describes who will handle your estate and who will receive your assets if you should die without providing your own written instructions in your own will). You have a choice to either prepare your own plan for the distribution of your assets, or rely on your state legislature to prepare your will.