agreed with greytone (and not just because my granddad worked for greyhound for 50 years) the NYT style manual, for example.
The New York Times Store > THE NEW YORK TIMES MANUAL OF STYLE AND USAGE
or the AP manual:
APStylebook.com
personal story- at a jury trial, mispronounced "slough" as sloff instead of slew thereby appearing to be a big city atty instead of a local.