You may have heard people say to update your will to ensure everything is accounted for. It would be more correct to say update your estate plan.
A will is not the only estate planning tool, and including an asset in a will that you have already dealt with elsewhere will only lead to confusion. As would failing to keep things up to date and omitting assets.
Here are some examples of things that should stay out of your will:
Anything with a beneficiary designation
The beneficiary designation will supersede any instructions related to that asset in the eyes of the law. Yet, you could still create problems if you say you want to leave a particular asset to a different person in your will.
Assets that typically use beneficiary designations are retirement accounts and life insurance policies. You can also set them up for things such as bank accounts.
Anything with joint ownership
If your house is in the name of you and your spouse, then they will typically take ownership of it all when you die. Saying in your will that you wish to leave the property to your children could confuse matters unless you clarify that it can only happen once your spouse too passes away. Take special care if your children are from a previous marriage, as they might not appreciate you leaving what they consider their inheritance to your new partner.
Anything in a trust
Once you put assets into a trust, they belong to the trust, not to you. You need to determine how you want to distribute them when creating the trust rules.
Estate planning is complex, and mistakes can be problematic, so ensure you seek legal help to get things right.