Study your audience

The Cardinal Sin in all business writing is to be Boring! So you have to start with something that will interest the reader, your audience. The cimoany financier needs to know why he should spend his money with your company when another is offering a similar product for half the price. The development engineer is interested in the price, just if it will serve his purpose.

You need to know who is going to read the document and why, what is on their mind. Once you know that just answer their question and you have them hooked.

Structure and style

The structure of the document should rarely change. Define the problem, address the problem and then tell the reader what to next. The style has to be not only readable but a compelling read. Be wary of using metaphors or humour if there is a chance of the white paper being read by readers of nationalities other than your own, they might not understand it or worse still they might find the comments offensive.
If you have any third-party (not customer quotes) evidence that can support the claims you are making in the white paper use them.

And don’t forget the summary, use it wisely and include a “Call to action” for the reader