I know for film, secrets are your best friend. The 'who, what, why, and how' questions keep an audience enthralled as you pull them from one scene to the next, but..
From the responses to my excerpt in 'Fragments and Feedback,' I gather that this is not exactly the case with material not indended for a visual medium?

"He drifted into the massive show floor of the furniture store..."

Chapter 1

Visual work can't do this. Everything has to be implied or said or shown, and the viewer must guess at it all.

If you are going to write something to be read, capitalize on the strength of written material and make motivations clear.

The one that's specific to written work (although it can occasionally be applied to film) is the problem of the reader feeling cheated. If you have a viewpoint character who tells the reader all about the embarassing thing that happened when they were nine and the texture of his shoelaces, it seems manipulative for that same character not to reveal his master plan for exposing the counterfeit beanie baby ring just for the author to drum up some suspense. In film this usually isn't the problem because (OK, Kathleen already pointed this out) you don't normally know the character's thoughts.

There is an analogue of this in film, though: An example of it is when a character whose perspective you've been sharing through much of the film sees something that is purposely hidden from the viewer. For instance, the character sees the murderer through a door, and gasps, "You!" The viewer can't see through the door because of the camera angle. Again, the danger is of making the viewer feel like information is being withheld that they would expect to have had if the writer weren't trying to force suspense.

The other danger, which seems as applicable to film as to writing, is that withholding information prevents the (screen)writer from being able to give all the interesting stuff to the viewer, so that the viewer loses interest. For instance, you could have a movie or story where an important (human) character is really an alien (granted, the idea is a little unoriginal in the first place), and gleefully write the whole thing, anticipating the reader/viewer's shock when the secret is revealed. But in the mean time the reader/viewer has no reason to care about the story unless the story is about the mystery of why Mr. Hooper, who otherwise seems so normal, eats borax with a spoon when nobody's looking.

The shorter version of the second paragraph is this: beware the story that's dependent on a plot twist at the end, because by the time you get to the exciting twist, you may have lost your audience. Not that this can't be pulled off occasionally.

Hope some of that was of some interest.

I cannot stress how much more important it is that the readers identify with the POV character than any degree of suspense you could possibly force. Likewise (although the rule is less hard and fast with film), a character that the audience is expected to sympathize with should remain in suspense whenever the audience is in suspense. Of course, the suspense does not have to come from having an identical point of view. For instance, if the character is acting according to some plan, the audience doesn't have to know the exact plan as long as there is enough danger or uncertainty for the character to share the sense of suspense.

Even in writing a detective novel, it is cheating for the POV character to know anything that is not revealed to the audience. This is one reason that all the Sherlock Holmes stories are written from Dr. Watson's perspective (the other main reason is so that Holmes can be portrayed by an admirer other than himself). One reason that the classic denouement/confrontation scene works is because the detective still has to confront the suspects with the evidence that he has collected before he can be certain of the guilty party, so that the reader is able to discover the information at the same moment that the POV character learns it. Another device is the trap to catch the villain red handed, which accomplishes the same purpose (although this scene, unlike the former, can be used plausibly for other dramatic purposes).