Hmm...I'm not above using the split infinitive (such as
boldly in to boldly go), and I
use slow and quick as adverbs as well as adjectives
(e.g. butcher him and cook him slow!). On the other hand, I do
observe the differences between they're (they are) and their
(belonging to them), it's (it is) and its (belonging to it),
and so on.

How do I manage all of these without sounding like a pedant
(in polite language) or a grammar Nazi (in more common usage)?
Perhaps you can answer that.