Translate the trip plan into flight segments
Write down the intended entry date, first destination, final destination and exit date before choosing flights. This prevents the reservation from dictating a trip that does not match the application.
For a direct return trip, the itinerary may contain only two segments. Multi-city travel can require an open-jaw route, such as arriving in one city and departing from another. Surface travel between those cities does not need to be disguised as a flight.
Choose plausible connections
Check whether every connection leaves enough time to change aircraft and, where relevant, terminals. Also check whether the connection introduces a separate transit requirement. The reservation should describe a trip you could realistically take if the application succeeds.
Airport codes deserve special attention. London, Paris, Tokyo and New York each have multiple airports. A connection that arrives at one and departs from another may require a long ground transfer.
Match the application record
Enter each traveller’s name from the passport data page. Avoid nicknames and do not silently substitute a different family name order. Dates should match the application form, accommodation plan and any insurance period supplied.
If the plan changes after submission, follow the instructions of the office processing the application. A reservation is evidence of intent at a point in time; it is not permission to ignore later requests for updated evidence.