I'm planning to run Memories of Holdenshire this week, and after having looked through the first Arc of the module it looks pretty cut and dry at first glance.
But, there are always things that crop up during actual play, and there are better DM's than me out there.
So, those of you that have run the module, did you make any changes to it or were there parts that you felt didn't work so well?
Is there anything you wished you knew beforehand?
I just started running Holdenshire for a 5 player group of optimizers. I moved it to the Delimbyr Region (Baldur's Gate) region of the Forgotten Realms and modified it so that we have the option of flowing into Descent into Avernus at 3rd level.
I changed the Khalikos (Sp?) to a Devil, and had all the characters wearing clothing tied to the Dead Three gods. This helps tie the story nicely into Realms Lore.
The adventure opens strong, but the rest of Act 1 is lacking substance. I found myself putting in lots of prep time to beef up the details for the starting town, creating some skill challenges for the boring fetch quests, and provided more context and story around the goblin "debt" encounter. Why are there goblins in town? What's their story? IF this gets into combat, what would the encounter layout look like etc.
For the wacked out doctor quest, I had the players conduct a skill challenge to assist him as he performed some shady surgery on another NPC to win him over. This provided a lot of fun and humor - also built on the brief description in the story about the "incident" Instead of a situation where the players walk in and pay for the yewbark, now each player must decide how to tackle the scene. Do they assist the crazy doctor? Do they persuade the doctor that there is no need to perform surgery? Does someone try to steal the bark while he is preoccupied?
I also had to think long and hard about what the players may have done when they were cultists for a few weeks. How will that impact play down the road? Will they run into more cultist "friends"? Were there others in the area that also may have been under the influence and now "free"? Maybe they run into another cultist on the road or worse...someone they wronged!! The story really focuses on the missed memories, but doesn't really dwell on the fact that they players probably did some fairly unpleasant things while they were a cultist. This allows you to foreshadow and use narrative tools at your disposal to tell a deeper story and tap into your players emotions.
One of my players is a paladin and was horrified to find blood on his sword when he awoke. Unbeknownst to him, he ended up stabbing the woman in the first scene as she tangled with the devil. When his memories come flooding back, he will later find out that he was her SQUIRE and romantic interest!
For the chase scene at the end of Act 1, I added some additional "chase" rules to make it more cinematic (think Indiana Jones) where the players are fighting from the back of a runaway cart, with the driver wounded and slumped over, contending with obstacles along the path ("watch out for that low tree branch!!!) while guards jump from horseback onto the wagon or throw spears.
You also should have plausible options if the players don't want to go with the NPC.
ACT II was a complete rewrite for me because I'm using the Forgotten Realms setting, but the Journey system was very helpful in planning that part out.
One thing I had to plan around was my Dragonborn's flight mechanic - it can circumvent obstacles so you have to be ready for that.
Sorry for the rambling reply, but I hope this was helpful and that your game is going well.