Begin by learning the flags of the countries you're most interested in. For instance, if you have family ties to the Balkans, start of with the flags of Albania, Bosnia and Herzegovina, Bulgaria, Greece, Kosovo, Macedonia, Montenegro and Serbia.
Learn flags that are commonly incorporated into flags. For instance, the flag of the UK is often found on the flags of nations it once controlled: Australia, the Cayman, Keeling, Cook and Coral Sea Islands and many others. Use the CIA Factbook's "Flags of the World" page (see References) to note these similarities at a glance.
Focus on common symbols. For instance, many Muslim countries incorporate the crescent into their flags. Countries that adopted their flags during Marxist rule, such as Angola, often resemble Soviet sickle and hammer imagery.
Try to learn the flags of the world by region or continent. Pay attention to regional trends, such as the bright flags of Africa that often incorporate green, yellow or orange and red.
Use the CIA's "Flags of the World" page to learn the flags of the world in alphabetical order. Try to focus on only four to eight flags while doing alphabetic learning.