What is etiquette for men with long hair at work?

It depends on the job. If it doesn't involve food or anything near food, then there is usually no etiquette to be done. However, if men with long hair work at a restaurant (or any other place that deals with food), the proper etiquette is to either wear a hat (if it is sort of long, but not too long) or wear a hair net (usually if it is really long). This is usually required for sanitation reasons, but is a common practice of etiquette.