I'm going to start running Hoard of the Dragon Queen for a new group, and we'll be playing our first session in a couple of weeks. As I've begun reading the adventure, the adventure hooks aren't great.

That said, my party has elected to start the game by not knowing each other, so I'm trying to put together a prelude adventure to bring the party together and hook them into the adventure. I've been thinking about a run in with some excommunicated cultists who are trying to steal enough treasure to get back into the cults good graces. However, I'm having a hard time figuring out how to hook the players into really caring about Greenest.

I'm hoping to put a high level outline together (just bullet points), so any ideas/structure the wonderful DM community would could help me out with would be much appreciated.

I was planning on doing something similar.  One quick thing to get them all to 2nd level, because Greenest would be much easier for them at level 2.  From all of the hooks they chose they all had a reason to "go to Greenest".  So the plan was to have them come together on the road and fate would have it that some cultists had an ambush set right at that spot to keep people from getting to town.  A similar idea was the characters come upon a group of townsfolk fleeing Greenest and pursued by kobolds.  

It was my first time running on Roll20 and I ran out time setting up the encounter so I skipped it.  It worked out fine.

Basically, if all the characters have a reason to be at Greenest, and they all end up with each other when they see the dragon and the attack, then I think you are good.  They need to get to the castle to find out what is going on, and along the way they can kill some cultists, save some villagers, or loot and pillage.  If you have planted the seed that they need to be in Greenest for some reason, then they need to be in the castle before the town gets completely wiped out (even though it won't get wiped it). 

If I may add another piece of advice.  The whole adventure flows well if you think of it as one long chase.  The characters are chasing the cult and the treasure from Greenest to the end.  After playing through it, I would have run some sections differently with that in mind.  Keep things moving, keep the treasure just out of reach.  

Thanks FoC! That is some good advice, and I'll see about incorporating it into my prelude session. I'm hoping to get a few ideas and we've them together. I'll be sure to let everyone know how it goes.

Spoiler alert: the problem isn't getting them to care about Greenest, because Greenest is hella exciting and full of combat, if they stumble across it they are going to want to head in there and save the day. The real problem is getting them to care about almost everything that comes after that, starting with following treasure halfway across the continent without taking it for themselves or killing the cultists, then doing the same thing at the end of the road at the roadhouse, then doing the same thing in the swamp, then doing the same thing at the lodge, then doing the same thing at the flying castle.... again and again and again that Campaign dangles a ton of cash and a straight up fight with bad guys in front of the party, and then tells them "for plot reasons, I need you to put the mission ahead of your personal greed, or instinct to explore off in another direction. No detours, no side quests, stay in your lane!"

That sucks, and unless you're a great DM at tricking your players into "deciding" to do things that they don't really have any choice in, HotDQ is boring and bad. Rise of Tiamat is better, because it properly frames the story in a way that the characters see a real reason they can't just faff off and be adventurers, and simultaneously opens itself up so that they can choose among alternative missions that all feed towards the same goal. Finding a way to make the players politically connected faction agents with a bigger mission very very early before the caravan can help, but really I think if there's ever a published campaign that you might want to rewrite the middle of to introduce more hexcrawling and sidequests, HotDQ is it. 

well in my case, it was a problem to get them into greenest because of their survival instincts :D

I think it´s best to start with some connection to Greenest to avoid that. I agree,that you need to put some hexcrawling and sidequests into it to make it more appealing in the later chapters and also the journey itself.

The Side Questing shouldn't be a problem. I used elements of character backgrounds during the low points in the game to help bring the world and characters to life for my players. Suddenly your best friend from childhood is on the run for stealing the from a baron, or your archer buddy who helped you get out of the life is now back to kill you for some reason; stuff like that.

I'm only through the Greenest chapter, so I'll read through a couple more chapters but really? Just following treasure around? That seems like a very lame introduction to the Rise of Tiamat. Huh.

I don't want to poop on it entirely, Tyranny of Dragons as a larger conflict/world state has real potential, but after Greenest HotDQ settles into a rutt with far too few dragons and far too much caravan duty, with the players playing a very small and very anonymous role in a problem that effects the entire region... and again spoilers, but ultimately nothing the players do in any way impacts the world as it exists at the start of Rise of Tiamat, other than giving some political powers a reason to like you and ask you for help. Googling around you can find some good suggestions for small tweaks to make HotDQ more fun for players as you go through it (or even total conversions, like merging it with Storm King's Thunder!), but the most straightforward fix that I can suggest without going too far into the weeds is to just involve the flying castle directly with the raid of Greenrest, have it take off with the treasure once it's done while the players watch helplessly, and then have them bring that info to some power players that are impressed by this info and put them on a mission to spend the next several levels side questing to follow up on sightings of the castle, strange cloud formations, or the dragon cult... rather than spending months following a wagon on foot, only to find out the highway the wagon is on leads to a dead end and literally only one possible destination (um), which contains a teleportation portal (uhhh?) which leads to a flying castle (uhhhhh!!!!) which flies things back in the direction of a physical location that's pretty darn close to where you started off in the first place (UHHHHHHHHHH!!!!!????). HOTDQ  as written makes zero goddam sense, and almost entirely squanders its promise of being about dragons and dragon hordes. But with the simple change of searching for clues/a castle instead of following a caravan you're not allowed to attack, the door is thrown wide open for the sort of side questing and typical adventuring that you're talking about doing. 

All fair points Chicken_Champ.  I encountered that party attitude when they got to the first Raider Camp, but I sorted out some things that worked.  My players raced to meet the treasure at Baldur's Gate and joined the caravan.  Then it was a matter or keeping an eye on it, getting information, and not getting discovered. 

1. At Elturel I basically inducted one of the characters into the Harpers, now I had a way to get and give information from the party at every inn and some other spots along the way.   So the characters felt like they were doing things.  

2.  The caravan was well run enough that unless the cultists were outed as such the caravan guards and master were keeping the peace.  So no overt action against the cultists would happen.  I also didn't let the players know all of the cultists, so they had to sleuth along the way.  As for action and fights during the caravan.  The players actively participated in a bunch of the encounters (hobgoblins, preytons, a bullette attack, undead popping up near Dragonspear).  Once the cult tried to take them out in the night, under estimating the players.

3.  I borrowed some of the side adventures that Dndbeyond put out for the Waterdeep to Baldur's Gate intro for Descent to Avernus, just in reverse.  

4.  As for the lack of dragons.  I used all the ones that were there.  The blue dragon, obviously, at Greenest.  Then there is a black in Mere of the Dead.  At that point the party was well known to the cult and I had Rezmir (with the help of the Black Dragon Mask and some of the treasure) "convince" him to patrol the swamp for the players.  Once the players were in the thick of it at castle Naerytar, he attacked and forced them to the caverns.   Finally the white dragon in Skyreach.  Throw in a dragon or two flying off and the distance and they got the idea.

So, I agree.  If you run in completely as written, it is a slog.  And I hit that with my group on more than one session.  I finally figured out the "feel".  Keep that carrot of the treasure dangling in front of them and keep them moving.  Interrupted rests because of night encounters, multiple fights in a day to deplete their options, and the reward of information (and some gold) kept my party going.  With the exception of one player new player we are all long time players and DM's, so that might have helped too.