I have a book that you might find interesting. It's: The Complete Plain Words; author Sir Ernest Gowers; second edition revised by Sir Bruce Fraser; publisher Pelican Books; 1975. ISBN 0 14 02.0554 3. It cost me 75 pence, but that was in 1975! It was first published in 1954, and has been reprinted many times since then. I'll give you a few chapter headings: How to draft a letter; Incorrect words and phrases; The choice of words; Jargon and legal language; Metaphors and other showy words; Choosing the precise word; Punctuation; Right and wrong use of the various stops (Apostrophe; Capitals; Colons; Comma; etc.) It's a handy reference book to have when you're not sure about where to put an apostrophe or whatever. I don't know if it's still in print, but it's worth asking at your local bookshop. Best of luck.