Prequels present a very interesting opportunity for writers. There is a story with a beginning, a middle, and an end. The end may not be locked into finality. That is, the end of a story is not always the end of the story unless everyone is undeniably dead, and even that does not always hold. No matter how it is sliced, that way lays sequels. Likewise, and somewhat in contrast, the beginning is almost never the first of any complete story, but instead the best starting point to tell what the writer wants to tell about the characters or situation that the work is to be about. When so desired it's easy to tell a story before another story. When these prequels are well done they take into consideration what happened in the original story in a satisfying way that adds depth to that original story, and at the same time draws strength from that originator, while still standing on their own.
I gave Paranormal Activity 2 a re-watch last night and was reminded I never did write the post about prequels I mentioned after the first time I watched it, so here we are. It definitely did its work as a prequel and even laid groundwork for the 3rd movie, which is a prequel to both--I have yet to see 3 but hear good things. Prequels have to follow one rule of sequels and that is to go bigger. There are a couple ways to do that. One is to have more and bigger scares. We are talking horror sequels here, but action sequels for instance would have bigger and more elaborate stunts. The other way to go bigger is to make a bigger story. That can be done by deepening the threat, widening or introducing a conspiracy, and generally raising the stakes. In horror the second story can also be more disturbing, which can be a part of either way to go bigger. It could be more gore, more violence, adding perversion, or making things more emotionally devastating.
When it comes to film there is little time to do the planning ahead to write what will be the prequel first and then write the original/first film knowing full well what came before. With published writing the pace required to do this is possible with some planning and a touch of time sacrifice. The question then is which method makes for the more powerful and engaging pair, trilogy, or series? Such a set of stories could delve further and further back into the timeline of a setting and it's central line of characters--whether or not that line is an actual family line or just interconnected characters carrying on some tradition or other non-familiar lineage. An interesting thing that could be done is to write flashbacks into the original book that are taken from a different point of view in the prequel or have a different spin on them with the difference being attributed to bias, missing detail, or failed memory in the original story. In TV in particular character bias between "actual" events and flashbacks or retellings is usually done with humorous intent, even in horrific series, but this is hardly a necessity and often unwarranted given the usual overall/mood.
Music: Music: Caught Somewhere In Time by Iron Maiden and At the End of the Rainbow by Hammerfall.