Are there any tricks to book multi-city international flights?

Another option that doesn't appear to be mentioned is to book a round-trip ticket from A->B, and a round trip ticket from B->C. The result is that you have an A->B->C->B->A flight with two return tickets, which often works out cheaper than booking one-way tickets or segments (in Europe/Australia/USA, not so much in South America, however).

If it's getting complicated, a travel agent or Flightfox (crowd-sourced expert search engine) might do it for you, as they generally have more knowledge on how to lower the prices and what's available. Of course, they'll also charge you for the service :/

Just want to share a few general tips:

1. Get any idea about how much it will cost to put everything on single ticket: Most travel websites supports multi city search. Just put down your itinerary and then search. Write down or print out how much it costs, and which airlines operates between cities.

2. Next, breaking up the itinerary into two roundtrips. A -> B -> A and B -> C -> B. If C is not a popular destination, or B -> C is dominated by a different airline alliance than A -> B's alliance, this could be much cheaper. Also, this could be a good option if B -> C has many low cost carrier options.

3. If you just want to stay in B once, then look for open-jaw flight for A -> B, C -> A, and separately an oneway ticket from B -> C. This could save money since you will fly less.

4. If B is a hub city, you can just search A -> C and see if there's any flight connecting at B. If there's one, you might be able to make B a "stopover". It's trickier to buy stopover fare online, but if you're lucky to spot one, the stopover fare could just be the same price as the roundtrip from A -> C -> A.

5. Use alternative airports: many people underestimate the importance of picking the right airports. If you're going to an international segment followed by some domestic trips, it's possible that all the cheap domestic flights are using another airport in the city. Don't forget to do your homework to figure out the right airport to search.

6. Oneways: this is less common for international flights, but in rare case the airlines just won't give you a good price if you buy roundtrip. You could just buy oneways for all segments.

7. Look for alternatives other than flying: if you're going to Europe or Japan, high speed rail could be another great way to travel. It's possible that taking a train is just comparable to taking a flight, and you might find the train fare more attractive.

To name a few sites that could help you figure out the above:

• Google flights: best for searching multiple city flight in one itinerary because of it's fast response time.
• Kayak: Great way to compare flight price from multiple sources.
• Vamo: specialized in multi destination trip optimization with most tricks above built in.
• Skyscanner: Great LCC coverage
• Rome2rio: Quick way to figure out transit options from one place to another
• ITA Matrix: A powerful flight search engine to find the flights and learn their fare rules.

You might also try booking a single A->B flight, and then combined B->C->A (if you are not really stopping in B on the way back).