I realize that the "header comment" format varies from programmer to programmer, but what would be an example of a "good" header comment?
Regarding formatting style, consistency is most important to strive for. Make sure every class definition comment looks like every other one, every method comment looks like every other one, etc.
So, if you're modifying existing code, make sure you follow their formatting style. The comments (and, to an extent, code) should look like only one person has worked on the file. If you're starting a new project, pick one style format and stick with it.
Places to start looking: