Identifying the modifier in a sentence is the first step to correct usage. For example, examine the modifier in this sentence: "With a microscope, John could see the nucleus of the plant cell." The first part of the sentence, "with a microscope," is the modifier because it provides more information about how John saw the nucleus. Modifiers may also be single words, such as adverbs: "Beverly sprayed air freshener only in the bedroom." In this case, "only" is a modifier because it tells where Beverly sprayed air freshener.
Sometimes it is unclear to what a modifier refers. In this case, it is called a dangling modifier. For example, examine this sentence: "After painting the walls, the room looked too dark." The first part of the sentence is a dangling modifier because it is unclear who painted the walls; it wasn't the room. Similarly, in the sentence, "Veronica could see the man sitting on the steps with the binoculars," it is unclear who has the binoculars. In this case, "with the binoculars" is another dangling modifier.
One way to prevent dangling modifiers in a sentence is to identify who is doing the action of the main part -- or clause -- of the sentence. In the previous example, the modifier "after painting the walls" implies that someone painted the walls. Clarifying this will eliminate the dangling modifier. For example, it could be rewritten to this: "After painting the walls, Hubert thought the room looked too dark." Now it is clear that Hubert painted the walls and thinks the room is too dark.
Sometimes the sentence needs to be rearranged in order to eliminate the dangling modifier. This may often be easier than trying to clarify the modifier in its current location. For example, "Veronica could see the man sitting on the steps, through the use of binoculars," is clearer than the original example, but the sentence is cumbersome. Consider rearranging the sentence to make it simpler and more clear: "With her binoculars, Veronica could see the man sitting on the steps."
In the single-word modifier example from above, "only" is placed near the phrase it is modifying: "in the bedroom." The sentence would be less clear if it were placed earlier in the sentence: "Beverly only sprayed air freshener in the bedroom."
Another way to eliminate the dangling modifier is by turning it into an introductory phrase. For example, look at this sentence: "Before planting the flowers, it was dreary in the garden." It is unclear who planted the flowers. The modifier -- "before planting the flowers" -- can be rewritten as an introductory clause to clarify the sentence. Revised, it might look like this: "Before Donald planted the flowers, it was dreary in the garden."