If you make a living trust, you might well think that you don't need to also make a will. After all, a living trust basically serves the same purpose as a will: it's a legal document in which you leave your property to whomever you choose. (The advantage of a living trust over a will is that property left through a trust doesn't have to go through probate court after your death, saving your family lots of time and money.)
But even if you make a living trust, you should make a will as well. There are two main reasons.
One big reason to write a will is that a living trust covers only property you have transferred, in writing, to the trust. Almost no one transfers everything to a trust. And even if you do scrupulously try to transfer everything, there's always the chance you'll acquire property shortly before you die. If you don't think to (or aren't able to) transfer ownership of it to your living trust, it won't pass under the terms of the trust document.
Second, a will can do some important things that a living trust document cannot. For example, in many states if you have minor children and want to name a guardian for them—someone to raise them if you and the other parent die before they reach adulthood—you must use a will. You can't use your living trust. You can also use a will to forgive (cancel) debts owed to you, something that isn't done in a trust document.
The good news is that if you use a living trust as your primary way to leave property, all you need is a bare-bones will. In it, state who should inherit any property that you don't specifically transfer to your living trust or leave to someone in some other way.
One kind of simple will is called a "pour-over" will, so named because it directs that all your remaining property be poured over into your living trust. That property must still go through probate on the way to your trust, however.
Making your will. For more information about wills, see the articles in Nolo's Wills, Trusts & Estate Planning section.
You can also use Nolo's bestselling Quicken WillMaker to make a valid will, as well as other estate planning documents such as powers of attorney and advance medical directives.