Curate, connect, and discover
I am enamored with the way that the writers of the brain tumor arc in Bones managed to have it be a twist while giving you multiple very strong signs that something was wrong by taking advantage of the fact that as the viewer you know you're watching a TV show. The first two times Booth hallucinates Bones points out that these are moments of unreality but the show couches them in the context of the episodes in which they occur so that the audience can easily and unconsciously dismiss them with their preexisting knowledge of tropes.
"Oh, well Booth was briefly unconscious in the process of getting a concussion. In television, situations like this are rife with characters experiencing dreams where their subconscious solves the case for them. Plus it's a clever way to include their cameo from Luc Robitaille."
"The show really wants me to believe that that really was a ghost that helped Booth and this is another instance of Booth being right about magic in the world while Bones is wrong, but even if I prefer that small space they leave for a little ambiguity, characters in life or death emergency survival situations on TV see visions of a person who's death they blame themselves for as a way to explore a characters relationship with guilt all the time."
And it's not really until both Bones and the show essentially say "screw the case of the week, something is Wrong" that you're, rather abruptly and forcefully, prompted to consider what these incidences might mean when put together, and it's not a very happy list of possibilities.
And while this post is about how well I think they preserve the twist by meeting people's expectations when they added the foreshadowing to avoid suspicion, it should be noted that I also think this is a great example of my belief that a good plot twist is telegraphed loudly beforehand, just in a code most people won't easily decipher.