Prepositions are words generally used in front of nouns and pronouns to show the relationship between those words and the rest of the words in a sentence. Source.
Adverbs are words that give information about verbs, adjectives, and/or other adverbs. Source. Correction: This post originally stated that there were two adverbs when there are, in fact, three.
Emily who was wearing red, looked at the door.Emily, who was wearing red, looked, at the door.Emily who was wearing red, looked at the door.Emily, who was wearing red, looked at the door.
Nonessential clauses add extra information to a sentence and are set off with a comma. Source
Who's phone is this?Whose phone is this?
"Who's" is a contraction that always means "who is" or "who has." "Whose," on the other hand, is used to indicate possession. Source.
You can affect the future if you put your plans into effect.You can effect the future if you put your plans into effect.You can effect the future if you put your plans into affect.You can affect the future if you put your plans into affect.
Though both words can be used either as a verb or a noun, "affect" and "effect" do not overlap in meaning. Source.
The sentence's subject is a noun that is doing something in the sentence. Generally, if you just look to see what is "verb-ing" in a sentence, that word is the subject. Source.
Timmy said, "I really love this TV show".Timmy said, "I really love this TV show."Timmy said", I really love this TV show."
Quotation marks are used to indicate direct quotes and are set off with a comma after "said." In American English, the period is placed inside the closing quotation mark. Source
I was studying in the library, you came in to join me.I was studying in the library.I was studying in the library, you joined me.When I was studying in the library, when you came to join me.
An independent clause contains a subject and a verb and expresses a full thought on its own. Source.
There are 23 helping verbs, listed here.
Walking along, cars were whizzing past.Walking along, cars whizzed past.Walking along, I saw cars whizzing past.Walking along, I saw cars whizzed past.
Since "I" is the subject, it should be placed immediately after the modifying clause ("Walking along"). Otherwise, it reads as if the cars are the ones doing the walking. Source