Numerical dates alone are prone to mistakes; you should include the day of the week, such as Saturday, Oct 5th. Most folks think in terms of names, not numbers. (e.g.: "Wanna go hiking on Sunday?" versus: "...on Oct 6?") This also forces you to verify dates using a calendar where discrepancies will become apparent.

Subject headers are the most important part as most readers will only look at the header to decide whether they will open the message. Plus, putting the date first allows sorting by date on the topica site or in your act-ma mailbox.

Take a look at the archived listings

Start with the date (e.g. 9/28) and end with the day (e.g. Sat)

Take a look at the archived listings to see the ease in finding an event if the correct date form is used.

Keep subject headers short and to the point, or they will be cut off, leaving the readers in the dark.
Moderators very often have to edit the headers extensively because they are:
- too long; the key point comes too late in the phrase and would be cut off
- contain irrelevant info and words (such as location, definite articles, 'event')
- lack recognizable content (names of non-famous people instead of title of talk)

Subject header examples that required editing:

original: The Abortion Access Project (AAP) seeks interns for Fall 2002.
problem: superfluous little words taking up space
[act-ma] Abortion Access Project seeks interns; Fall 2002

original: Curmudgeon: CARP Panel Deconstructed
problem: cryptic acronym, useless info]
[act-ma] 9/23 Webcasting & Freespeech/Curmudgeon (Mo)

original: 9/22 Make Art for the Local IMF/World Bank Demonstration (Sun.)
[problem: longer than necessary]
[act-ma] 9/22 Art-Making f. IMF/WB Demonstration (Sun)

original: 9/25-26, Scott Ritter in Cambridge (Wed-Thurs)
[problem: unfamiliar name (in 2002), no indication what it's about]
[act-ma] 9/25-26 Scott Ritter: Iraq war wrong (Wed-Thurs)

You must double check phone numbers before you ask your readers to call e.g. a senator by verifying those numbers (call yourself, or check the person's website).

Always include web links to your organizations. Don't waste that easy access opportunity. The prefix http://www. makes a web address clickable in most email browsers, hence it's much more likely that people will actually go there.
(Some programs recognize the short form www. but http://www always works.) AND: This allows the person posting to check whether the link actually works, so write those hot links and TEST THEM.