“Start at the end.
What you want the recipient to do.
Not to think, to do.
Begin by writing the conclusion with a desired outcome action.
What do you want the recipient to do after reading it.
Having written that, consider what the necessary prerequisites are to make them see that as the only possible reasonable cause of action. Then flesh those out.
Next consider what “common sense” or memeplexii you have conflicted with – and fix it so you don’t. Competing with existing memplexii is futile. You will lose. For example:If you say, cryopreservation won’t work – no matter how reasonable your grounds, you will lose the attention of the cryopreservation enthusiasts.
If you say “Better than God” to an Christian, his existing memeplexii will immediate turn you into a missionary of Satan…etc.
At this point, writing an introduction should be easy. All you have to do is examine your “supporting” paragraphs and then write a suitable passage explaining why these points are important (i.e. why you have inserted them).
It is preferable if, in the introduction, you can introduce the idea which you would like action taken on. People are sheep and typically have terrible comprehension skills. Telling them, I am going to tell you, followed by telling them, and summarizing with “Do this” stands a much better chance of being understood and acted upon.
This “bottom-up” construction method has the immense benefit of avoiding the temptation to follow extraneous threads and confuse the issues.
Try not to accomplish more than one aim in a single letter, else you will just confuse the recipients.
I would add, that it is always much easier to precise the work of, or advise others than to deal with your own work.
So forgive me for not always living up to these high ideals :-)£”