Grammar mistakes people often make

A lot of people like to often split their infinitives.
And you musn't begin a sentence with 'and' or use a preposition to end a sentence with.

Clever.

Prepositions? Here's a joke.

First day of Harvard, a country boy on scholarship asks a fellow student, "Where's the library at?" The fellow student, appalled at the poor grammar, lectures the country boy. [I'm shortening this part of the joke, but you can fill in your brand of upper crust]. So the country boy rephrases, "Where the library at, a**hole?"

There is nothing wrong with split infinitives, its perfectly natural in English. The only reason some people think they are bad is because they think English should use Latin grammar rules which is ilogical to say the least. Even my Oxford dictionary says splitting infinitives sounds less awkward. The only problem is when writing you often have to avoid splitting them, because someone will read it and say 'oooh, split infinitive, this person writes like a 3 year old or mark you down for it'.

Now about leaving prepositions at the end of a sentence...

For what reason would one do that? To what is the world coming. To where are we going. From where are you?

-Yet another ilogical latin rule, even the Oxford agrees this form of English is awkward and unnatural and the rule needn't be followed when the sentence's meaning is clear.