Add a comma after "teach", to make it read a more clearly. Without a comma, the reader might start to read the sentence to mean that someone is teaching the skill of praising positive actions, rather than praising positive actions being a way to teach. Does that make sense? Otherwise, your sentence looks ok.

Is the best way to teach to praise positive actions and ignore negative ones? Delete "it." The word is not necessary and does not refer to anything in the question.

Nothing wrong with it :)

Seems OK to me.