1. Booking Your Flight
The sooner you book your flight the better. I recommend not booking your ticket at least than 3-4 months out, if not more. The farther out you book your trip, the more likely it is your flight will be cheaper. The closer you wait, the more it will jump! Germany has two big tourist seasons: summer (July-August) and then winter (December). Try to book a bit before or after these months.
September is also a big tourist season, thanks to Oktoberfest. Any attempt to come during this time and you will pay hefty prices for airline tickets and hotels, especially anywhere near Munich.