Be careful when using pronouns, especially “it” and “this.” Often these pronouns will be substituted for a real noun and can cause awkward sentences, vague references, passive construction, and wordiness. Compare:
- It is the time of year when the leaves change color.
“It” in the above example is vague reference that renames nothing. Try the sentence with a real noun:
- Autumn changes the color of the leaves.
Notice the economy of words, the active verb, and the actual noun. Anytime you use the word “it” in your sentence, ask yourself what is “it”? Chances are that you could use a real noun in place of the ambiguous pronoun to make your sentence more specific and much easier to read.
Wordy and weak:
- It took Menaleus a long time to get home.
Cleaner and more precise using the subject and verb where they belong:
- Menaleus took a long time to get home.
Wordy and weak:
- Gorgias believed that it is impossible to objectively perceive anything because people cannot look past their opinions.
What does “it” tryly stand for? Use the real subject:
- Gorgias believed that objective perception is impossible because people cannot look past their opinions.
"It" vs. "Who"
In many instances "it" is in place of where "who" should be, and "who" is in place of where "it" should be.
When using a title for a specific function of a person, "it" should be used instead of "who".
Example: "The builder will stop after it has received the check."
Although it seems strange, this is the correct use of "it".
Besides "it" sounding weak and wordy, rules where it is supposed to be used should be considered.
http://english.stackexchange.com/questions/95289/when-to-use-it-instead-of-who. "When to Use "It" Instead of "Who"". English Language & Usage. 23 December 2012. 4 November 2014.