Number 1: ‘Mind ya P’s and q’s’
Origination of phrase:
Most printers of the older generation will tell you that 'mind your Ps and Qs' was a common expression in the composing room, where apprentices were prone to confusing lowercase Ps and Qs when setting or dissing type (putting it back into the type case). Type sorts are a mirror image of the letter they print and they're set upside down in the composing stick, so it's a very easy mistake to make even for experienced comps, so all very confusing.
The common usage today is roughly equivalent to mind your manners, or as a more specific reminder to say please and thank you. It's quite a jump from the composing room to this modern use, but it wouldn't be the first idiom to change its meaning over time, and you can imagine older comps delivering this mild reprimand to their children without giving it much thought. When it's your turn in charge, it's amazing how you find the voices of authority from your own youth suddenly speaking from your lips, and I certainly remember having this told to me when I was younger and now passing it onto the next generation!!!!