I lead weekly Sunwell PuGs, starting off with a trade chat ad macro similar to, "Let's blow the doors off the [Sunwell Plateau]! Need a tank, two healers, and dps -- come get your achievement, maybe a rare recipe, and open rolls on all drops!" The linked achievement is the first impression you can give to someone that you know the raid.
That ad attracts four kinds of people: the rare person who hasn't gotten their achievement yet, the completionist recipe seekers (At least one drops almost every run. Often two or three drop.) people looking to gear up for both their 70s and for roleplay, and people who want the legendary bow for the achieve or for whatever reason.
Each time someone gets on board, I ask them in raid chat what role they want if they haven't already told me, and then I mark their role accordingly (right-click, choose role, etc.). When I fill a role's capacity, I alter my trade chat macro to not ask for that role, plus I vary my lead-in sentence. Little touches like that show your experience. So, my next variation may be, "Come take a tour of the [Sunwell Plateau]! Need one more healer and some dps -- get your achievement, maybe a rare recipe, and open rolls on all drops!"
When Sunwell is a popular raid on a server, you can reserve gear. If your server is like mine, there's little interest in the raid. Offering up gear for open rolls attracts more people who would otherwise ignore the ad.
When I have everyone (and it has to be everyone, to prevent loot drama) ready to go, I say, "Loot rules are as follows; open rolls! That means greed everything, and need on upgrades or RP gear." If the PuG seems friendly, I might add "We do have some lower levels looking to gear up, and I'd love to see them get a couple of pieces". I never mention twinking, because while many 80-85s really are happy to help carry some 70s through a raid if the 70s remain gracious, the word "twink" brings up too much baggage with too many people.
Be very careful not to spam trade chat repeatedly. Keep a respectful interval between your postings.
Most importantly, don't tolerate bad behavior. When you do get bad behavior, it usually comes from your dps, not your tank or heals. One bad apple can ruin a raid, so always overstock your raid with dps in case one drops or you need to eject one. If someone objects to having "too many people", tell them you want a couple of extra in case something happens and one or two need to go, because no one will want to join a half-complete raid. That usually backs off anyone looking to run slim.
Tell them you'll explain boss fights before they happen, and keep the explanations short. For example:
"For the first boss, do NOT dps right away. Wait until the portal comes up, everyone pile in, and we'll burn down the shadow boss to minimal health. Then when we get back out of the portal, we'll burn down the dragon."
"Otherwise, the boss bugs, and we have to wipe it. Clear?"
"Second boss is tank and spank, but don't stand next to each other after he dies. Otherwise you'll spread fire to your teammates. And do NOT pull the dragon when she appears after the second boss dies."
Now, for loot. I don't master loot, but rather keep the rolls open just like a normal instance run. This does three things. First, it makes life a lot easier for you. No need to ask for rolls, and resolve who got what. People know that it really is luck of the draw. Second, it makes it look like the raid is chock full of loot. 13-15 people running a 25-person raid? Stuff drops almost every pull. Third, you can roll last, and that way you can see who is winning the loot, and if someone is abusing the system by needing on everything, and so forth.
If someone starts complaining about not getting loot or unfair loot distribution, I say that there's more loot to come, and that they're welcome to try to negotiate with any loot winners for gear they really want. Sunwell is one of the raids that you can trade BoP gear to any raid member for two hours after winning the gear.
Next week I'll lead my 14th PuG Sunwell on my 74, thanks to Felmyst STILL not dropping the pants I need. I built up a few regular recipe hunters who know me now, as well as a couple of 70s who understand how to be respectful about getting carried, so that they can gear up. Likewise, I've gotten to know a couple of rude mooches and a couple of "I know it all and try to usurp the raid" types, and I steer clear of them.
On the worst days, people pick at each other and bicker, and mess up boss encounters because they're not listening. As long as you have enough dps and heals, you'll still finish. On the best days, the raid runs like butter, loot drops left and right, everyone's excited, and at the end they ask you if you're going to run anything else.
At which point you take them to Black Temple.
