The Digital Reader had a piece on their website entitled: “Infographic: 15 Grammar Rules You Learned in School That You Can Break With Impunity”

I’ve picked out some of the more interesting ones below.

1. Never end a sentence with a preposition:  This one is from the ark and is probably the most broken rule because of how formal sentences become when the rule is followed.  For example: “From where do you come?”
2. Know the difference between who and whom:  Who refers to the subject of the sentence and whom refers to the object.  In colloquial speech, it is common, but incorrect to ask; “Who did you invite?”
3. Never describe a singular noun with a plural pronoun: An exception could be, “Somebody left their hat on the train” – when the gender of the somebody is unknown.
4. Use the correct verbal agreement for a collective noun:  Collective nouns describe groups of things acting as a single identity: swarms of bees; teams of people – “The team is going out to lunch”.  “None of us is invited to the wedding.”  Right but sounds wrong.
5. Do not split infinitives: Infinitives are verbs in their most basic form, usually preceded by to.  But the following is OK: “She tried to quickly think of an awesome sentence.”
6. Avoid vague pronouns:  For example: “When Jess picked up her baby sister, she was so happy.”  Was it Jess or here sister who was made happy?
7. Use That and Which correctly:  That and Which are both relative pronouns that introduce clauses; the difference being That introduces a non-specific clause, and Which introduces a specific clause.  A specific clause specifies the identity of the noun to which it refers; a non-specific clause only provides more information.
8. Use the correct personal pronoun:  Me, myself and I all describe oneself but cannot be used interchangeably.  I is the subject of the sentence; me is the object.  Myself is a reflexive pronoun when the subject and the object are the same.  Example: “Sue smiled at herself in the mirror.”
9. Use Farther for physical distance and Further for figurative distance:  Example:  “We had run farther today to catch up with out teammates who were further along in the training schedule.”
10. Use Fewer and Less correctly:  Fewer is an adjective used to quantify nouns that can be counted; whereas Less is an adjective used to quantify intangible nouns that can’t be counted.  Example@ “Fewer coins, but less money.”
11. Into is directional, In To is a verb phrase:  Example: “Breaking into the museum” should be written as “Breaking in to the museum.”

And three rules that should never be broken:

1. Apostrophes:  Apostrophes show possession and contractions and that’s all!
2. Affect vs Effect:  Affect is a verb; Effect is a noun.
3. Don’t make us new words, unless your name is Shakespeare.  Some linguists believe that English has up to 300,000 distinctly usable words.