Keep your modifying phrases close to the nouns they modify.
Something is not quite right with this sentence:
Nobody is allowed to dump anything here except city employees.
Can you see the problem? Who can dump? Or who can dump what (or whom)?
The phrase 'except city employees' is a modifying phrase. It modifies 'nobody' - not 'anything' presumably! - so it should remain close to that word, the subject of the sentence:
Nobody, except city employees, is allowed to dump anything here.
Or better:
Only city employees are allowed to dump anything here.
Here the modifying phrase is attached to its noun, and not dangling.
Another example:
By manipulating the lower back, the pain was greatly eased.
This sounds like the pain itself was doing the manipulating. A correct version would be:
By manipulating the lower back, the therapist greatly eased the pain.
Here 'the therapist' is the subject of the sentence. He/she both manipulates the back and eases the pain. The 'By..' phrase is a modifying phrase.
And one final example for you to work out:
The nurse handed the baby to the father in pink pyjamas.
Who is wearing the pink pyjamas?
For more see this page. The example at the top of this post comes from this site. A non-dangling version would be:
