- What’s the large puzzle and what are the smaller pieces/puzzles/evidence?
You have to have the main puzzle – the game played by the murderer and his threat to blow up a major building if he's not paid a billion dollars. The smaller puzzles are his way of playing the game, giving clues to catching him beforehand. Another example is any Bond film. The big wealthy bad guy planning on destroying the world and the minor bad guys Bond kills to lead him to Mr. Big. (by the way, Mr. Big was the bad guy in Live and Let Die.)
- Make the main character interested in puzzles or solving problems.
If you have an auto mechanic who only enjoys fixing cars and drinking beer thrust into a murder mystery with lots of clues and pieces to join up, then the story may not work because the character doesn't care about solving the crime. If he does care, then he'll struggle much more than is necessary and you'll lose reader interest. I think some of the best stories are when the bad guy is familiar with the detective. He knows the good guy likes games so the bad guy tries to devise the perfect plan to foil his opponent.
- Get the details correct. Continuity, logic, etc.
Make sure the evidence and the clues point in a direction. I'm not saying you can't fool the detective (and thus the reader), but in the end, the evidence should link up.
- Focus on the middle of the story. Everybody knows the beginning and the ending, but the middle sometimes has problems.
I put a star next to this point. Where does a story usually bog down? Between the opening couple chapters and the ending climactic ones. You have to keep the reader's attention by throwing in challenges and action scenes. If all the detective is doing is sitting around his office, thinking, then readers will get bored. “But wait,” you say, “this is what Nero Wolfe did all the time. He rarely every left his brownstone.” Sure, but that's what Archie Goodwin was for. He was the gofer. He'd visit the suspects and the femmes fatale.
- Read in the genre of what you are writing to know how to write it.
If you're not familiar with medicalese, your doctor story will have serious flaws. But beyond basic knowledge of the subject matter, you have to know how to write a thriller. They are different from a straight Ellery Queen murder mystery.
Next week, the final five on plotting the thriller.