Regardless of the time of day you decide to fly, the ticket price will remain around the same. Book flights from Doha to Waterloo, Iowa as you normally would.
Related info for your journey
Useful info, stats and facts about Doha to Waterloo flights.
These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Doha Hamad Intl Airport to Waterloo Airport flight would often be abbreviated as a DOH to ALO flight.