How do you deal with unsolicited parenting advices?

Smile, nod, noted with thanks. If possible, try to change the topic to something else if you are unable to go off without being rude. haha.. sometimes it may be good advice even though it was "volunteered" by the other well-intended individual. So it's good to keep an open mind when it comes to such things but also remember not to let it bother you if it is not applicable (especially if the person is not fully aware of the situation).