This Hacker News discussion provides lots of in-the-trenches wisdom about how to write more-effective emails. (Hacker News is probably the premier discussion site for techies.)
Here are some of the more-interesting takeaways, interspersed with some of my own practices:
1. BLUF: Bottom Line Up Front (from the military) — this might include saying in the first paragraph, e.g., “JANE, please see the request in #5 below.”
2. Short paragraphs.
3. Numbered paragraphs for longer emails, so as to signal changes of topic.
But keep the paragraphs short — use unnumbered continuation paragraphs if necessary.
4. REQUEST: For key paragraphs, use the first word in all-caps as a signal, e.g., RECOMMENDATION; REQUEST (as in this paragraph).
5. All-caps the names of people who should pay particular attention, e.g., JANE in #1 above. (Or, use @Jane.)
6. Be careful about wording, so as not to appear curt or harsh.