Start with one region, not the whole world
Two hundred flags at once is a wall. Twelve flags of South America or fourteen of Oceania is a short list you can master in an evening. Choose a region in the flags mode, set it to Easy and play until you get a full round right, then move up to Medium. Only after two or three regions does the world set start to make sense.
Play both directions
Naming the country of a flag and picking the flag of a country are different skills. The first asks you to recognise; the second asks you to tell four similar designs apart and is much better at fixing details in memory. The mixed variant alternates them question by question, which is why it is the default.
Learn look-alikes as pairs
Most mistakes come from a handful of pairs: tricolours in the same colours, Nordic crosses, red and white bands. Learn them together, with the one detail that separates them, instead of as two separate flags. Our guide to telling look-alike flags apart puts the usual pairs side by side.
Use the mistakes list
At the end of every round the quiz lists the questions you missed, with the flag and the answer you gave. Read it before starting the next round: it is a ready-made revision sheet, and it is always about the flags you personally confuse.
Keep it short and regular
Five minutes a day beats an hour on Sunday. The quiz of the day has two flag questions every day, and the expeditions below have the largest flag legs of all 180, a good way to mix flags with maps and capitals.