When I uploaded my spoilers, I wanted them to be grouped together, but what should the main essay be? That is when I thought I should make this up. When I send one of my spoilers to someone, they sometimes wonder why in the heck I will make up such of a long document, and how I achieve it. So I decided to type this far smaller thing up.
First of all, I don't just write a spoiler for its sake. They are a pain to make, so a lot of motivation is required to do one. Perhaps the film isn't well known, as Like Water For Chocolate is. Or the plot is confusing, so I put all the clues together for the audience, as for Spider. Or I just like it a whole lot, which is the case with Luther. When I feel the motivation, I do the following in preparation.
Before writing the actual spoiler, I might go ahead and type up an intro and/or an initial, basic draft for an appendix if desired.
I work in cycles. First, with a paper and pencil in hand (I have a crappy chalk board which I use as a table on my lap), I watch usually two DVD chapters at a time. If they are short, I may do three; if one is really long, just that one. During this, I put down everything I can observe and remember as important from my earlier viewings. Next I type it up in my word processor file, while the movie is still playing in the background . Who knows, I may think of something and it also helps me with the flow of the spoiler. When done, I use spell check and do a quick reread. Then I transfer it to the HTML document and delete it from the other file. If I feel the need, I rewatch a scene until I feel I got enough of the critical info done. If it is a complex but important scene, I watch it well over 5 times if necessary.
While doing this, I also note all the characters mentioned by name. When they do, I note his or her role in the movie, and place it into the list of characters. I also delete the name from the list I got from IMDB. That way I know who I have or have not got.
Once every chapter is done with the HTML document, I finish any appendixes I need and call it the first draft. I then reread the whole thing and note anything that I can add, foreshadowing things I missed, or scenes I might need to clarify. And so, I watch the whole movie one more time - yes, you heard correctly, while reading my spoiler at the same time. After that, one more check for revision and then I consider it done.