You can’t use “and” to start a sentence
Actually, you can use and for this purpose. Just for good measure, here are a few examples from literature:
“And even Mary could assure her family that she had no disinclination for it.” – Jane Austin from “Pride and Prejudice”
“And to seek to make the blacksmith a scholar is almost as silly as the more modern scheme of making the scholar a blacksmith.” – W.E.B. Du Bois from “The Souls of Black Folk”
“And let every other power know that this hemisphere intends to remain the master of its own house.” – John F. Kennedy from his Inaugural Address on January 20, 1961
You always use commas after each item in a series
Commas are necessary after each of the items in a series, except the last one. For example, someone might suggest that this is correct: red, white, and blue. However, that’s not the case. Using the comma after “and” is actually redundant. It’s like saying “and” twice. So, the correct method would be to write it as follows: red, white and blue.
Over and under
They do it in commercials and advertisements all the time. I suppose it is for brevity sake but that doesn’t make in any less incorrect. I’m talking about when people use the words “over” or “under” to indicate anything other than height. For example, cars are not on sale of under $20,000. Nor are there over 7 billion people in the world. The correct phrasing for each of these would be: Cars are on sale for less than $20,000 and there are more than 7 billion people in the world.
It’s not a real word if it’s not in the dictionary
First off, this implies that there is only one official dictionary when in fact there are many. On another note, there are many words that have simply been removed from dictionaries based on infrequent or rare use in modern language and conversation. I bet you wouldn’t find a lot of terms used in the Renaissance era in today’s dictionaries but that does not make them any less relevant.
Improper grammar is never acceptable
Generally speaking, improper grammar is a bad thing. However, there are a few exceptions. One of the first that comes to mind is with the use of direct quotations. Whether the quote is from a real person or a character in a book, language and grammar allowances can be made for such things as accents, education level, etc. A quick example is the phrase frequently spoken by the character Aibileen Clark in the film “The Help” in which she says, “You is kind. You is smart. You is important.”