As time progresses and the entertainment industry slowly runs out of ideas, the notion of prequels has begun losing consumer appeal. What was once a creative alternative to sequels, spin-offs and...well...brand new stories with unique characters is becoming a surefire last resort for those wishing to cash in on established success. While prequels have much to offer when done well, more often than not they are carelessly put together and the end result is lackluster. This is partially due to heavy reliance on fan knowledge and support, and largely due to writing backwards being less forgiving than writing forwards. To write a good prequel, one must be talented in all the ways he or she would write any engaging story. However, they must do so with even more limitations, awareness, and demand for surprise.
Time is the writer's primary confines. Care must be taken to maintain accuracy and continuity with previous lore (future events) without threatening to alter thresholds in the timeline. The timelines themselves can pose a problem if significant historical events that were previously alluded to are neglected, or if such events are created for the sake of current plot and are then, chronologically, wiped from future lore via character ignorance.
Another issue of time is settling on the start of it. Going backward from a point, the writer only has so large a window to create a compelling tale (assuming the character is human) before an overlap or parallel occurs. The focus, then, is locating the exact moment in a character's life wherein she becomes interesting. From here it is a matter of creating a series of events to aid in a reverse-arc. The original character is dissected, mangled, and ran through the gamut (figuratively, and at times, literally!) to make sure it undergoes enough change to be considered dynamic and interesting...yet winds up in exactly the same state her future self. In essence, we have to uncreate a character backward.
New characters must also be introduced with caution and their influence monitored. Importance must be such that their existence is crucial to current story progression, but not so much that their absence in future events would go unnoticed or unmentioned by the main character. There are obvious solutions for characters who fail to make appearances later on, solutions which many readers and viewers see coming a mile away. This is an inevitable technical flaw. Concerns should lie in two places specifically: allowing new characters to have an impact in the current story, and making their impact resound in future events. This could be adopted vernacular or mannerisms, skill sets, scars, trinkets and items, or memories. For these reasons, it is a good idea to have every character's history in mind—where they've been, who they've known, what they've done—despite in what order said character appears in the chronology.
Perhaps the biggest technical flaw of all is regard (or lack thereof) for the main character's safety. The audience already knows our character survives to take place in future events. Why, therefore, should they be concerned at all for her health and well-being? For all intents and purposes, the character is immune from death and her success, in one form or another, is guaranteed. This is where strong character building and storytelling come into play, and also where many prequels fall short.
Rather than manifesting a literal theme park and throwing beloved characters on a series of rides to thrill the audience, the writer cannot be lazy and forsake one of the most important rules: Make the reader CARE. To do this, sometimes the character has to be reinvented from the ground up. Her path to the state of mind in future exploits must consist of more than petty action sequences and memorable (or not-so-memorable) dialogue. It must consist of very real emotional struggles, impossible decisions, forged friendships and severed bonds. The audience must be forced to forget that our character survives her obstacles...and one of the best ways to do this is by reminding them of that character's humanity through loss, suffering, and physical pain.
So long as we can relate to and feel something for a character, the mere fact that they survive becomes a moot point before long. By that time, it will become clear that the character does not arrive at her future incarnation physically or emotionally unscathed.
