Sentence structure, or Letting people know what's coming

I've had editors worry about putting a comma after introductory phrases (an open punctuation style would put the comma in, a close punctuation style would omit the comma). A more interesting problem is what to put in that introductory phrase.

Let's look at that. Of these three sentences

Press F7.
Press F7 to save your document.
To save your document, press F7.

I prefer the third.

The first sentence is the worst because it gives the reader no clue as to why they should press F7. Without that information the reader is unable to incorporate their own judgment. If, for instance, this sentence appeared in a tutorial the reader wouldn't know if they could skip this step.

Sadly, sentences like this get written because many writers believe that readers process their tutorial from the first step to the final step. This isn't true, of course: Readers use tutorials to meet their own goals and they do that by modifying the steps of the tutorial (c'mon, you know that's what you do, too). But what's true of tutorials is true of most technical writing: readers need to take what they're given and modify it to meet their own needs.

The second version is better because the reason is included. But the reason is given at the end--I won't find out "why" until I've read the whole sentence.

I prefer the third version because it may be that, to meet my goals, I don't need to save my document--or, at least, don't need to save it right now and would prefer to skip the step. I like the the third sentence because it begins by signaling what problem/point/issue it addresses. Given that information, I can skip the rest of sentence if I'm not interested; conversely, when I am interested in a particular problem/point/issue, having the sentence begin by stating that it addresses that point makes it easier for for me to find that information.

And I'm not even going to discuss whether information makes more sense when the "reason why" is given first (but I bet it does).

Reading or read

• The Day the Cowboys Quit by Elmer Kelton