Here's a few basic hints:
- Put the actions in bold and have short paragraphs.
- If you are trying to agree on a date/time for something, provide several options and ask everyone to 'Reply All' with their preferences. If they can make none of the suggested dates, ask them to propose 2-3 preferences.
- Keep a record of the replies in a text file on your desktop as the replies come in.
- After a few days, email personally (forwarding the original thread) those people who have not yet replied.
- Avoid asking open questions ('who wants to bring what?') to a group email. Instead operate like a wedding gift register and give people the specific options, perhaps even suggesting who does what.
- Once all the info is in, send out a brief and clear email that is clear in the subject line and the body of the email what exactly has been decided.