We help a lot of clients set up their limited liability companies.  As part of our services, we draft an operating agreement for their LLC.  If they have a corporation, we draft bylaws.  Both of these documents are the "internal rulebook" for how the company's owners (shareholders/members), managers (directors) and officers deal with each other. 

Crumpton Law has a terrific blog post on a court case where the operating agreement was vital to resolving a dispute between two members of an LLC. But many of our clients  are the sole owner, officer and employee of their company.  That's number 8 in the 33 Things A Business Planning Attorney Can Do For You -- "Avoid misunderstandings about agreements between shareholders or members." 

But when the member, manager and officer is all the same person, how important is the operating agreement?  John Cunningham's answer is "Very important."  His post on how operating agreements can help prevent "piercing the corporate veil", that is, making the owner liable for the company's debts, is valuable reading.