An overview of various providers of flights, besides cheap flights also quite normal charter flights to Prague, see for example the many links in the Flugzentrale.de.
Direct Flights to Prague include companies from Germany to: Lufthansa, German Wings, Czech Airlines and TUIfly.
Also keep in mind before a flight ticket purchase, if the airline awards as part of a program Miles, and whether you will be credited with the miles in your program.
In Prague at the airport the terminal is 2 for flights to and from Germany, Austria, Switzerland, used and the other countries of the Schengen Agreement.
At the airport in Prague you can grab a snack with drink, and it is recommended, to make smart previously because of the foreign currency exchange. In Prague there as in the whole Czech Republic officially the currency of the Czech crown.
Often, you can pay in Euro, as it is often possible at border crossings, but the price is often characterized by 10-15% higher, than if you would pay in the local currency. Therefore, it is also at Prague Ruzyne airport exchange offices, where you can exchange cash. However, we recommend, to differentiate the Czech crown on which to place ATMs at the airport.