Writers frequently employ a Rule of Three -- three characters, three plot lines, or three uses of a motif. (See what I did there?) You'll find it everywhere in legal writing, and not just because we like to cover all bases as if we were paid by the word, as in the standard language in many wills: I hereby give, devise and bequeath. Or marriage vows: love, honor and cherish. The idea is that just one thing is a bit random, two establishes a bit of a pattern, three cements that pattern and four (or more) is over-kill. So, for many purposes, three is the sweet spot.
In my last WIP, I had three goals for the protagonist: meet a deadline for her day job, harvest the garlic on the farm she's just inherited, and get her aunt buried properly (which then becomes a larger goal of seeking justice for her aunt by finding her killer). In the quilt appraiser's story, the protagonist had three goals: solve the murder, prepare for a career-making/breaking speech, and deal with a health issue that complicated everything.
Recently, though I was reading the thoughts of John Barnes here, where he says, "I like to set up seven slightly related ideas and riff on them till it adds up to something." Perhaps because I was brainstorming a new WIP at the time, I loved the idea of expanding from my usual focus on three to finding seven things that all contribute to the overall story. His Rule of Seven includes more than plot-lines, or the story might get a tad chaotic, and it serves as a reminder that plot-lines and other elements all work together, so the parts come together for the whole that's larger than their sum.
For my current WIP, I already had: 1. genre, legal thriller, 2. premise involving abuse of civil forfeiture laws, 3. a non-mystery-related deadline involving mountain biking, 4. the basic genre goal of solving the mystery, 5. the protagonist's desire to change careers and become a hobby farmer, and 6. a health issue for the protagonist, complicating her other goals.
The two things I was missing (which would add up to more than seven, but I'll combine one of them with another element) were: an interesting title (reflecting the genre), and something compelling about the antagonist.
Whether I'll succeed with the title and the antagonist is still to be determined, but simply knowing where to concentrate my brainstorming efforts was useful. It should save me a lot of the angst I usually experience when I've got a bunch of words written, only to realize that there's this big, gaping hole in the story where a three-dimensional antagonist should be.