• Use the four Cs of effective communication: Clear, Consistent, Convenient, Compelling
• Identify your goal and be as specific as you can
• communicate to the right audience a message that will appeal the interest
• highlight key messages
• have a clear understanding of your message and be prepared for questions
• use facts not rumors
• communicate with empathy

I would first identify the most appropriate person or group of people or department who has experience or expertise in the project I'm asking them to commit time to developing, or providing funding for, committing resources or providing constructive feedback for. Then I would write the benefits of the program or project but integrating what the project or program will do or provide when completed if the funding, resources or manpower time commitments are provided or authorized. I might also add a few examples or point out what would or could happen if the funding, manpower or resources were not provided or authorised.

When writing a message to a client or internal stakeholder in which I must ask for a decision that will require significant commitment of their time and resources, I begin by asking specific questions that are crucial to the project or situation's success. With the use of positive language and succinct arguments, I prepare a well-organized note that is concise and to the point. It must be made clear as to what we can expect to happen with each decision made, both good and bad.

Identify your target and highlight different topics based on this. As you mentioned the language will be different, for example business and legal do not speak in the same way. Ask specific questions, do not have the floor open to generic replies. Foster emotions to stimulate reflections and then comments.

Found this today - good read https://jerz.setonhill.edu/writing/e-text/email/