The manuscript I’m currently working on is chock-full of sentences that begin with phrases using the present participle (-ing), and a lot of them read in ways the author doesn’t intend. I thought I’d offer a quick-and-dirty explanation of how to avoid some of the most common problems associated with those phrases, in case it’s useful to any of you.
First, don’t open a sentence with an -ing phrase unless the action occurring in that phrase happens at the same time as the action in the main part of the sentence (or unless you’ve included a word like “after” to clarify the timing). The following sentences don’t work:
Unlocking the door, she left the room.
Walking toward him, she placed her hand along his cheek.
Do you see why? You can’t unlock the door and leave the room at the same time, and it’s highly unlikely that you would be placing your hand on someone’s cheek while walking toward them. Such sentences need to be reworded.
Also, when you start a sentence with a participial phrase, that phrase needs to modify the subject of the main clause. This sentence is also incorrect:
Nearing unconsciousness again, his head slumped forward.
It really isn’t his head that’s nearly unconscious. To make this correct, you’d need to rephrase to say something along the lines of “He neared unconsciousness again, and his head slumped forward.”
I hope this helps someone!