How you manage the guild-first kill is just as important as managing a wipe.
Just after the victory:
1.) Take the time to celebrate.
Don't start barking orders or calling for loot rolls as soon as the boss hits the floor. Take a few moments to celebrate with your raid. Savor the accomplishment. Be just another raid member for a little while. You've earned it!
2.) Emphasize teamwork.
You may know in your heart that if the main tank hadn't stance-danced that last fear so quickly or if that druid hadn't solo-healed the last 10% of the fight, you'd be toast -- again. But this is not the time to point out such things. The lesson your raid needs to take away from the experience was that, first and foremost, excellent teamwork won the day. Feel free to whisper people or send private messages congratulating them for their outstanding individual efforts, but do it later. Guild firsts are a great bonding experience. Let the raid feel the love as a whole.
3.) Thank -- and remember -- the people who were there.
If this is a boss who has given your guild fits, be sure to acknowledge the people that sacrificed their gold, time, and energy to face an encounter that most assumed would end in failure. Everyone hates that guy who "disconnects" for the night after a wipe or two on a tough boss. That person can bring your raid to a screeching halt. A guild cannot progress without people willing to bash their heads against a wall for a few weeks until everything finally clicks. Don't undervalue such people. Take note of who showed up for the wipefests and who only started coming after the boss was on farm. That will tell you whom you should be bringing along for new content in the future.
4.) Get the loot right.
Everyone who was there will remember who got what, and everyone who wasn't there will want to know. So take your time and make sure you follow your own rules and system to the letter. The raid will be patient with you as they ride the wave of euphoria. So wait until you're able to focus on the task at hand and avoid an embarassing error that can taint the victory.
5.) Take pics!
It goes without saying, but take some good screenshots of the kill (and the killers) for posterity.
When the raid is over:
6.) Discuss why you won with your officers and class leaders.
Just as you need to identify why you're wiping on a boss, you need to figure out exactly why you were successful this time. Don't do this in /ra or /g. You'll risk insulting someone and souring the night (i.e.: "I think we won because Soandso wasn't there pulling aggro."). Keep it in /o or, better yet, post in a private forum so you can look back on the discussion the next time you're up against this boss. There's always room for improvement, so don't forget to talk about what could have been done better, too. Now that you're over this hurdle, make sure you can repeat the success next week.
7.) Use your progress to bolster recruiting.
If you're looking to add some members, now is the time. Guilds that are stuck on bosses aren't nearly as appealing as guilds that are mastering them. So advertise your progress. Don't be obnoxious about it by spamming the Trade channel in Shattrath. Put a big notice on the front page of your Web site. Then post about the kill on your server's forum. Most servers keep a list of raiding progress by guild. Make sure your guild is on that list and make sure your info gets updated. People on the server who are looking for a new raiding opportunity or a change of scenery may be on the lookout for guilds that are progressing through the content they want to see.
What does your guild do after guild firsts? Whatever you do, I hope you have the chance to practice it soon!
Send Scott your guild-related questions, conundrums, ideas, and suggestions at firstname.lastname@example.org. You may find your question the subject of next week's Officers' Quarters!