Don't dangle your modifiers
A dangling modifier happens when two parts of your sentence become dislocated grammatically. It’s an easy mistake to make but an important one to avoid — otherwise your sentences could leave your readers confused.
First, a bit of background. A modifier is a word or phrase that changes or adds to the meaning of another word or phrase. For example, I could write:
“After weeks of procrastination, I finally got round to writing this blog post.”
As well as being true, this sentence is grammatically correct. The modifier here is ‘after weeks of procrastination’.
The problem comes when you try and link two parts of a sentence that don’t have the same subject. Take a look at the following example.
“Driving through the forest, a bear walked out in front of my car.”
In this example, the modifier ‘driving through the forest’ is left dangling because grammatically it can't refer to anything except the bear, which would be absurd. If you wrote this sentence, you’d be saying that a bear driving a car somehow walked out in front of your car.
What can you do to fix it? You can give the modifier a phrase with the same subject to attach itself to. Here you’d say:
“Driving through the forest, I saw a bear walk out in front of my car.”
But perhaps a better solution here would be to rewrite the modifer so that it no longer needs to be connected to something:
“As I was driving through the forest, a bear walked out in front of my car.”
I find that I’m more likely to leave modifiers dangling when I haven’t properly thought through a sentence before I start writing. So I’d say make sure you plan ahead and then, when you’ve finished, check everything through for things dangling where they shouldn’t.
And if you’d like to know more, Oxford Dictionaries have written an in-depth blog post on participles and how not to dangle them.