About Sigrosenblum's suggestion that you study "Elements of Style" I would like to direct you to not, as support for my saying Elements will lead you astray I offer this
http://chronicle.com/free/v55/i32/32b01501.htm. It is a critique of "Elements of Style" by Geoffrey Pullum, the head of linguistics and English language at the University of Edinburgh and co-author of The Cambridge Grammar of the English Language.
He tears "Elements" apart.