Make sure to keep it non-controversial, unless, of course, you are eyeing some short lived media attention and long lived grudges.
Don’t let the text be loud, allow the sub-text to rule the mood.
Sit with your family and friends more often. Observe them closely and ask them for old-forgotten memories.
Visit the significant places you have ever been. In all likelihoods, you would find some new thing and recollect some nostalgia.
Click a lot of photographs and keep all the albums handy. Devote a lot of time looking out at the pictures; the childhood pics, college pics, marriage pics, ceremonial pics, holiday trip pics, family pics etc.
Divide the events of your life in some chapters and treat each chapter as a separate entity, an al-inclusive one.
Get a basic hold on Microsoft Word (or any other tool that you prefer for the similar application).
Keep a diary with you; if you are well versed taking notes on your smart-phone, it will be as good if not better.
Make a schedule of writing; aim to write daily. In the scheduled writing hour, prefer to not do anything else; even if you are suffering with writer’s block of the day, don’t keep the pen down. You can anyway refine the raw notes at a later stage.
Keep breathing space in your writing schedule. You have to be at your thinking best so offering yourself deadlines serves no real purpose.
Talk to your old friends, and if they allow, record their conversations about your togetherness.
Always keep a backup of your soft copy.
Tie up with an editor, and explain him about the job before you press the ‘hiring now’ button.
Buzz your social network about your progress in writing the biography. It will keep your close ones informed and you might get some motivation by their comments and feedbacks.
Keep the narration simple, and don’t breach its integrity.
Refrain from using opulent, flowery words. The aim is to ensure an easy comprehension.
Avoid going high on artificial stimulants to get a high (read excess coffee, tea, alcohol, nicotine); the flow is just the best when you are truly in pulchritude.
If possible, start each chapter with a theme quote. The quote can be your own. PS: I am using this strategy for my own biography.