Grammar Cop: "it's, its"

I'll be sure to cover that one in the future!

I must admit, I am a sucker for good grammar.
My unsolicited grammar tip of the day: 'who' is for people and 'that' is for things... eg. I have a friend who is cool and a dog that is clever.

What about 'tis?
Archaic but acceptable. 'Tis a contraction of "it is."
It is.

I must admit, I am a sucker for good grammar.
My unsolicited grammar tip of the day: 'who' is for people and 'that' is for things... eg. I have a friend who is cool and a dog that is clever.
Thanks for the excellent contribution.

Knowing the rules of using "a" and "an", why isn't it proper grammar to say, "He is a F.B.I. agent"?

Because phonetically, the letter F is spelled EF, thus there's a vowel sound at the beginning and "an" is required rather than "a".
Unless you were being sarcastic or otherwise making a joke and you know all this. It's hard to tell with text.

Because phonetically, the letter F is spelled EF, thus there's a vowel sound at the beginning and "an" is required rather than "a".
You got it!
Since a few people follow me, I thought it only fair that I give them something. American English grammar is one of my few strengths, and so I'll share some things periodically. My hands tremor, so this is difficult, and I'll try to keep them short.
These two words, "it's" and "its" are commonly mixed up. The problem seems to arise because the English possessive is normally noted with an apostrophe, as in "That was Kant's mistake." But English also uses an apostrophe for contractions: as in "Kant can't (an abbreviation of can not)."
One easy way to keep them straight is to keep in mind that "it's" is a contraction of "it is," while "its" is the third person gender neutral possessive pronoun. You don't use an apostrophe going from "he" to "his," or from "she" to "her", so don't use one going from "it" to "its"
It's easy if you remember its history.