Antilapse is your situation when somebody named in your will dies before you do. To cover yourself, you should consider naming a contingent beneficiary (a backup beneficiary) for any property distribution in your will. You can include words such as:

In the event that my named beneficiary for the property listed herein does not survive me, then I hereby direct that that my bequest be given to John Doe.

If you don't make your own provisions for contingent beneficiaries, and if your state has an antilapse statute, then that law dictates who receives the property. (The property has been in limbo because of your beneficiary who died.) If your state doesn't have an antilapse statute, then typically the in-limbo property goes to the beneficiaries you name in your residuary clause. (That clause names the beneficiaries who get anything you haven't explicitly mentioned in a giving clause.) Sometimes, though, that is exactly what you want! Be sure to work with your attorney to determine if naming a contingent beneficiary makes sense.