There are a multitude of grammar rules and many have exceptions, but there are ten basic rules you definitely need to know that can make a big difference. 

Essential Punctuation Rules for Good Grammar

1.Periods always go inside quotation marks. This rule doesn’t apply to all other forms of punctuation.

2. Use a hyphen in compound adjectives that come before nouns. For example, write, “A ten-year-old girl won the prize” or “The girl who won was ten years old.”

3. Apostrophes don't form plural nouns. Apostrophes are for contractions and show ownership. Angie’s car. .

Usage

4. Another essential grammar rule that most people forget is: don’t use pronouns without first stating antecedents. This means, before you us the pronoun, before you have clearly stated the word the pronoun refers to in the previous sentence. Instead of “I went to the registration office and they said…” Better: I went to see the registrar, and she said I needed to return on Friday.

5. Don't begin a sentence with “which” unless it is a question. If you try to begin a sentence with “which” you are unable to form a complete sentence. It is used to add to another clause. Ex. My house, which has been in my family for years, is now on the market.

6. Use “who” to refer to people. Use “that” for things. Ex. My neighbor who is in the at- risk group for the virus, stays inside no matter what. Instead of : my neighbor “that”...

7. If you use “not only”, then use “but also” in the same sentence. This rule also applies to neither/nor, either/or, both/and

8..Place a comma before “and” when it joins two complete related ideas.

Ex. I went to CVS and the grocery store (no comma because there is no complete sentence after “and”). “We decided to split up to cover more ground. I went to CVS, and my husband hit the grocery store.” (Place comma after “and” because there is a complete idea on both sides of it.)

Mechanics

9.  “A lot” is two words and it is better to use a synonym to avoid overuse or lack of specificity. For example. Instead of saying she talked “a lot.” Say, “She talked nonstop.”

10. Indent to create a new paragraph for three reasons:

a. When you change topic: When the facts, information, details, or ideas shift to another facet of the topic.

b. When you change setting: A shift in time, location, mood, day, date, direction, or space alert readers with an indent.

c. When you change speaker: Every time a character (dialogue) or individual (quote) speaks, a new paragraph is needed.