In most states, you create an LLC simply by filing "articles of organization" with your state's LLC filing office (which is usually part of the secretary of state's office) and paying a filing fee. A few states refer to this organizational document as a "certificate of organization" or a "certificate of formation." Most states provide a fill-in-the-blank form that takes just a few minutes to prepare. You can obtain the form by mail or download it from your state's website (check your state's secretary of state or corporations division home page).
A few states impose an additional requirement: Prior to filing your articles of organization, you must publish your intention to form an LLC in a local newspaper.
You'll also want to prepare an LLC operating agreement, though it isn't legally required in most states. Your operating agreement explicitly states the rights and responsibilities of the LLC owners. The main reasons to do this are to clarify your business arrangements and to decide how your LLC will be run. If you don't create a written operating agreement, the LLC laws of your state will govern the inner workings of your LLC.
You can use a self-help book or software program to guide you through the process of creating personalized articles of organization and writing an LLC operating agreement. For more information, see Nolo's articles How to Form an LLC or 50-State Guide to Forming an LLC.
To form your LLC right now, use Nolo's online formation service, which will collect the required information and file your articles of organization with your state.