Most LLC owners skip the operating agreement, the contract that sets rules for decisions, disputes, and adding members. Without one, your state's default laws take over, and they're usually worse for your business than custom terms would be.
Chapters
One of the most common mistakes I see business owners make when registering LLCs is not having an operating agreement. An operating agreement is an essential document that basically sets forth the rules of your business. The operating agreement will set forth things such as what to do when there's a dispute, how to add members and remove members, how to raise money from outside investors, what to do when somebody dies, and a lot more. Operating agreements are especially important if your LLC has multiple members because it'll set forth and get everybody on the same page with regards to how disputes and voting will be handled. Even if your LLC does not have multiple owners and you're a single owner of the LLC, it's still important to have an operating agreement because if you don't have one, then your state's LLC Act will automatically apply, which is usually not in your best interest. I personally wouldn't want the state's default rules to tell me how to raise money for my business, how to add members, or what to do if there's a dispute.