At Balticon this past Saturday, I watched a panel about Creating Tension with Scott Andrews, Mark L. Van Name, Gail Z. Martin, and Chuck Gannon.
All agreed that for tension to work, the threatened character must be relatable and the stakes recognizable. Maybe summarize the details of what would happen if All Was Lost.
Andrews: It is best to end a chapter with a cliffhanger to keep the reader engaged. Disquietude can act as cliffhanger by using awe, mystery, or curiosity. Entering an awesome new environment can pull the reader into the next chapter. The reveal of an important question can pique curiosity.
Van: Lee Child says unanswered questions keep the reader on edge. In foreshadowing a menace, heighten tension through proximity. For example: the threat is first mentioned, then later detailed, then seen at a distance, then when the protagonist has to hide from it. Morbid humor works, for that read the memoirs of soldiers.
Gail Z. Martin says that Jim Butcher novels will almost resolve a conflict completely, then introduce a last complication.
Gannon says that tragedy is two honorable characters working toward opposing ends (he made clear this was not an original thought, but I can’t remember who he was quoting). Trust your instincts above any plot formula.
Other panels reinforced reading Romancing the Beat and Save the Cat.