The movement of your story comes from the way you stack your images, whose creation we discussed in I is for Imagery. Readers–whIch is to say, human beings–create story the ways kids play with blocks. Give a reader two images and she’ll find a way to connect them, determine some possible relationship between them. If indeed we intend a relationship between two images or moments of action or observed details, we need only place them side by side for the reader to quickly determine their connection.
Selecting your key images and then juxtaposing them creates tension, engagement: story.
Contrast is another part of the magic of juxtaposition. Juxtapose what a character says with what s/he thinks, or what s/he says with what s/he does. The tensions unearthed there propel a story forward.
A Practical Alphabet for Writers: Find all the letters so far at https://bookwritingworld.com/blogs/