As the SCAP was written month by month by Paizo, it is likely that events that happened in later chapters were not known to writers of the first chapters.  This can be seen by looking at the original maps of Cauldron, which did not have the proper top-down views of House Vhalantru and House Rhiavaldi.  In order to better foreshadow coming events, here are some ideas that were put forward.

Adimarchus Dreams - These dreams are for the Dream haunted character.  They allow the characters to understand Adimarchus and how he ended up in Skullrot.

Chapter 1

• Introduce Vhalantru as a patron of the group (or a single PC)

Chapter 4

• Capture of Scarred Soul Character - The Last Laugh captures and tortures the character with the Scarred Soul trait.  The group then rescues the character, allowing them to gather information from the encounter. 
• Shebeleth entrance - One of the Thirteen Cagewrights actually takes over the Church of St Cuthbert.

Chapter 5

• An ambush by the Necrocants foreshadows a guest at Thifirane's party

After chapter 6 

• Navalant goes hunting for the real Vhalantru in Sasserine (Vhalantru from Sasserine side-trek)
• Gau Kleeoch finds mention as PCs get deeper into trouble

Chapter 7

• Attack on the Church of Kord - Sheb's scheme to weaken Cauldron's religious orders unfolds.

The Alternate Villains area also have a lot of foreshadowing ideas.