Another common situation is the one where a windward boat is about to be pushed over the starting line by a leeward boat. Leeward hails "up up up" while the windward boat replies "Hey, you are pushing me over" and stays put.
In this case, I recommend heading up just enough so that you have to bear away to avoid contact. Then hail "protest" and foot away. Don't let the windward boat disrupt your start any more than necessary but make sure he did actually fail to keep clear (which is more than not responding to your hail).
Regards,
Eric
