That is classic Hercule Poirot.

Write an outline, filling it in and correcting it as your ideas develop and change.

Use a big white board or cork board with lots of connections, like a conspiracy theorist.

Write by hand whenever you can, pencil is better than ink.

When you get stuck with the actual writing, tweak the outline and play with the connections.

Listen to good actors read early to mid 20th century short stories and mystery novels.

No, I do not write fiction, but I do some writing.

Work backwards.