Save the booking page as it appeared when the contract was made. Keep the standard information form, contract confirmation, terms, invoices and the booking email. For a telephone contract, record what was said and request the documents on a durable medium.
Add all communications about visas, passports and health formalities. Preserve messages with sender, recipient, date and time. If the information changed after booking, document that later development separately from the information available when the contract was concluded.
A useful timeline covers the booking, documents supplied, application, authority response, withdrawal, organiser response and payments. The booking-flow article helps determine whether several services formed one package travel contract.