Book when your schedule is clear, don't wait for a "cheap day"
There is no fixed cheap day of the week for fares. Airlines sell by fare bucket: when the lower bucket sells out, the price moves to the next one. So the surer approach is to book when your schedule is clear, especially for Tet, summer and enrollment-season flights.
If you are not in a hurry and want to wait for a better price, tell the booker to switch to fare watching: HVSC tracks the itinerary and notifies you when there is a significant change.
Baggage: ask first, don't guess
Each airline counts baggage differently: some by weight, some by piece. Within the same airline, a low fare class may not include checked baggage. Buying extra when booking is usually cheaper than buying at the airport counter.
Always keep power banks in carry-on baggage. Liquids in carry-on on international flights are limited by volume. Food and medicine taken to another country must follow the destination country's customs rules.
Connections: one ticket or two
When the sectors are on the same ticket, checked baggage is usually sent through to the final destination, and the airline is responsible for getting you onward if the earlier sector is late. Combining two separate tickets may be cheaper, but you bear the risk of missing the flight and may have to collect baggage and check in again.
Some countries require a visa or electronic authorization even when you are only changing planes. The booker checks this requirement against a Vietnamese passport before choosing the connection point.
Documents: check your passport expiry today
Many countries require a passport valid for at least 6 months from the date of entry. On domestic flights, adults carry a valid citizen ID card or passport; children have separate rules by airline.
The name on the ticket must match your documents, written in uppercase without diacritics. Sending the booker a photo of the passport information page is the fastest way to avoid a one-letter mistake.
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