Working with students in English classes, I encourage them to take risks with content, experiment with structure and be extravagant with (appropriate) vocabulary choices. This makes the process more enjoyable for them as a writer, and less tedious for me as the reader!  My one exception, however, is use of the apostrophe. Used correctly, the apostrophe reassures me. Thrown about wherever a word ends in the letter ‘s’ just upsets me. An apostrophe is an apostle of the grammar gods, sent to do one of two things. If you don’t know what either of those things are, don’t use it.