Here are two more theories, there are many others.

To mind your Ps and Qs is to be careful; cautious.

The Ps here are said to be pints and the Qs to be quarts. The publican “chalks up” or “puts on the slate” the drinks supplied to customers; they must be aware of how much they have drunk or their bills will be unexpectedly large.

OR

It is derived from the printing industry as a suggestion to an apprentice to be careful where the danger of confusing lowercase “p” and “q” was increased because typesetters had to view the typeset text backwards.

Two popular theories revolve around the mirror-image quality of the two letters. The phrase was recorded in 1830 as meaning “to learn one’s letters.” It was aimed at children learning to hand-write the lowercase letters p and q, which are quite similar. Another explanation along the same lines comes from the world of printing. Typesetters used blocks of type that were mirror images of the letters, so it would be easy to mix up lowercase p and q. This origin would give “mind your Ps and Qs” a connotation of being careful and paying sharp attention.

Another oft-mentioned source of the phrase is old pubs where beer and ale was served in pints and quarts. The barkeeper tracked patrons’ drinking totals by marking “P” for pints and “Q” for quarts. Both the barkeeper and the drinker would want to keep careful track of those Ps and Qs so they knew what the final bill would be. Also, the drinker might want to pay attention to how much he drank so as to keep his own behavior under control.

World Wide Words notes that this puzzling and quirky idiom has inspired some fanciful explanations. In the 17th century, the expression “P and Q” meant “prime quality,” which might have influenced the Ps and Qs phrase. Some suggest the saying came from a French dancing master’s instructions to perform the dance figures pieds and queues properly. Or it could be an admonishment to sailors to keep their navy peacoats clean around their tarred queues or pigtails. But these derivations seem pretty far-fetched.

It meant “mind your pea (jacket) and queue.” Queues (pigtails) were often powdered, and wifeypoo was telling hubby to keep the cruddy kid stuff off his collar. An even dumber variation of this involves “pieds,” French for “feet,” and says minding your p’s and q’s means combing your hair and polishing your shoes, or something like that.

P and q stands for “prime quality.” According to the Oxford English Dictionary, to be P and Q was a regional expression meaning top quality. It first shows up in a bit of doggerel from 1612: “Bring in a quart of Maligo, right true: And looke, you Rogue, that it be Pee and Kew.”

Possible sources:

“This expression, meaning “be very careful to behave correctly”,

has been in use from the 17th century on. Theories include: an

admonishment to children learning to write; an admonishment to

typesetters (who had to look at the letters reversed); an

admonishment to seamen not to soil their navy pea-jackets with

their tarred “queues” (pigtails); “mind your pints and quarts”;

“mind your prices and quality”; “mind your pieds and queues”

(either feet and pigtails, or two dancing figures that had to be

accurately performed); the substitution of /p/ for “qu” /kw/ in the

speech of uneducated ancient Romans; or the confusion by students

learning both Latin and Ancient Greek of such cognates as _pente_

and _quintus_. And yes, we’ve heard the joke about the instruction

to new sextons: “Mind your keys and pews.”

The most plausible explanation is the one given in the latest

edition of Collins English Dictionary: an alteration of “Mind

your ‘please’s and ‘thank you’s”. ”

–http://www.yaelf.com/aueFAQ/mifmindyourpsandqs.shtml

So originally, Mine your P’s and Q’s. Was “Mind your peas and queues”. And meant “Don’t get your uniform dirty with your hair dye.”

That’s exactly what it means, to mind r manners! But where P & Q’s comes from is beyond I & R’s lifetime. Be Good so to speak! The sylables have O to do with Manner’s. Maybe someome on Moonshine

made it up wayyyy back & couldn’t Spell! ha

Are U minding r P’s & Q’s?

LOL, Diana D

I know it sounds stupid but that is what i think!

it was from pubs in ireland a long time ago. People would start to get drunk and get very rowdy. So the bartender would say to them “mind your P’s and Q’s”. Which meant for them to mind their Pints (P’s) and Quarts (Q’s), or in other words, to mind how much they were drinking.

please dont beleive the people above bacause they have no clue what they are talking about