I strongly recommend to authors of tell-all, autobiographical books (or other books that refer to living people) that they seek a legal opinion before going to print. A good lawyer probably won’t have to read the book in its entirety, particularly if you provide a copy in which you have highlighted the instances where you name living people or organisations (e.g. individuals, bands, companies, clubs, government departments, etc) and where people may be identifiable. This process will reduce the time the lawyer needs to spend on your project and will, therefore, reduce the cost to you. 

In most cases, you will need to make sure that you have the permission (in writing) of each person you actually identify, if you provide personal details about them. It depends entirely upon how much detail you are giving about the individual or group. If it is material that is already in the public arena, authors have been reasonably safe in the past—but given that the 'public arena' might now include spurious comments on nefarious websites, don't take risks.

A lawyer can help you with a watertight legal disclaimer, as well.

The legal aspect is probably the main reason we see so few autobiographies from younger people—if you’re 80, most of the characters in your book will probably no longer be in a position to sue the pants off you. And your grandmother won't still be alive to read the book and disinherit you for your wayward behaviour!

Before sending your book to a market assessor or editor, I recommend that you go back through the book and look at how each chapter ends. Aim to make the conclusion of each chapter pithy and punchy, humorous, surprising, or full of pathos—anything but tedious! Don’t leave your reader feeling bored or frustrated, or with endings that simply trail off. After all, you want to lead your reader into another chapter. 

Don’t be afraid to rework chapter endings. This may actually involve moving the contents of chapters around so that they end on a better note. Read the end paragraphs of each chapter in isolation. Do they make you want to read more, or do they make you want to go and put the kettle on?