do you correct or not......?

Just to clarify what they said and give them a hint, I politely restate what they said giving the meaning in another form

If I can understand what they mean, and I know for a fact it's what they mean, no I do not. What's the point. We know the meaning. If the meaning is ambiguous or makes no sense otherwise, I would correct them as to clairfy. I am a teacher, and in the classroom I def. correct students, but when talking to their parent no I do not. I just make sure that I use correct diction, venacular, syntax, etc. in hopes taht they catch on!

If someone voluntarily requests that you correct them, do so; otherwise, it's rude to correct them or even offer to correct them. When you offer unsolicited language correction in informal situations (such as normal conversation), you're regarded as condescending, or even hostile. Don't do it.

Yes I do. That's how you learn the language.

How else will they know how to speak correctly unless someone corrects them. Do It.

yes i correct them

Yup, they usually don't mind =] So i will correct them

yes i correct them if he or she would like correct themselves

Depends on the person but by default no...

Absolutely, they may not know!

But be polite about it of course ;D