Things to NOT do...
1. Don't wait until the 6th person joins to change it to a raid... 6 times in a row
2. Don't let level 4s in your group
3. Don't ask people to share the quest
4. Don't let members of your party go off and run level 3 quests.
5. Don't leave your LFM up for hours at a time, hoping 11 other people will spontaneously take leave of their senses.
Things you SHOULD do...
1. Keep a low profile, and try to join other groups until you've learned the quest.
2. Use spaces in your LFM description.
3. Work to build a reputation as someone who keeps the worthless pile-ons out.