1. when making announcements in your comm, don't forget to email the participants about it. don't assume that they always check their friends page because 75% of the time, they don't.
2. if a participant doesn't reply to an email you sent in 3 days, email said participant again. if she still doesn't reply overnight, then panic and consider her a dropout.
3. remember that a mod is any fic challenge/contest/exchange's first line of defense. be prepared to pinch hit.
4. always send 2 reminder emails before a deadline -- the first, a week before the deadline, and the second the day before the deadline.
5. always acknowledge that you've received a draft or a submission from the participant.
6. a period of inactivity longer than 3 days is bad. if you have to delay posting or reveals, then let the participants know. post an announcement in the comm; it's better than making everyone wait.
7. participants and readers want complete transparency, so always let them know what's going on (even at the risk of sounding obnoxious; they'll appreciate the info, anyway).
8. never reply to emails in a bitchy tone. it just makes you look and sound a crazy, overly invested fan who takes herself too seriously. be civil and strict, but never be a bitch.
9. humor is a welcome addition to any community announcement or an email. it helps participants feel good about joining the contest/exchange, knowing that their mods aren't robots.
10. always thank participants who've made it until the very end. they're the very reason your challenge/exchange was a success. they deserve the credit.