If you are relatively young and healthy, your will should be simple enough to draft on your own. There are several self-help books and software programs that can walk you through the process step by step. If you think your affairs are in order and your situation relatively uncomplicated, then you should be able to adequately prepare your will without the help of an attorney. Lawyers can cost you several hundred dollars, and they mostly use templates similar to ones that you can find online.
There are a few instances where seeking the help of a lawyer would be beneficial. If you have a complicated family situation such as children from more than one marriage or ex-spouses or even same-sex partners, hiring a lawyer will ensure that your affairs are handled in the way you intended. Attorneys can also assess if a simple will is the best way to handle your individual situation. For example, if you have assets that equal more than $1.5 million, your assets will be subject to estate taxes and you may need to consider a different type of estate planning so your loved ones don't have to pay those taxes.
Having an attorney is also handy if you fear that someone close to you may contest what is in your will or even your mental competency in preparing it. Having an attorney will give validity to your requests.