IF IT'S TOO GOOD TO BE TRUE, IT PROBABLY IS!
When searching for flights for an upcoming trip to the Galapagos, I used Kayak to help me set my expectations. Those were destroyed when I realized that Kayak was showing me fares not really available. Check out this one:
Looks good, right? This is their "hacker fare." So you book two one way flights separately. However, when you click "view deal" to be taken to purchase, you'll see immediately that Avianca's lowest flight is $227 one way. This was problematic for me because it doubled my budget for this flight. I was expecting to pay around $300 total, ended up paying almost $500! Make sure to go directly to the airline to see prices.
KEEP IN MIND THAT MANY LOCATIONS DO NOT ALLOW YOU TO FLY IN ONE WAY, AND YOU MUST HAVE A RETURN TICKET HOME BEFORE ENTRANCE
This is also true of the Galapagos, you cannot technically book a one way flight to Baltra Island as a foreigner. This is often true of pristine locations that are being protected by their governments from tourists becoming ex-pats!
ONCE YOU FIND A GOOD PRICE, MAKE SURE TO CHECK OUT THE AIRLINE DIRECTLY
Never just book! Make sure to do a review of the airline you are considering. When flying internationally, expect most of your airlines to be headquartered in the country that you're traveling to or the country with the largest international hub that transfers you to the smaller location. This means that what you eat and the comfort expectations will be set more by the culture of that nation than your own.
For instance, while flying China Air, we found the seats to be quite small, more like seats in economy on a domestic flight within the U.S., but while flying Aer Lingus (an Irish airline), we found the seats to be more similar to business class on a domestic flight within the U.S. Additionally, all the food options on China Air were Chinese oriented, while Aer Lingus was Western oriented. The food wasn't terrible on China Air, but each option in economy was fish, beef, or chicken "with brown sauce." This might be important if you have dietary concerns, which you can take care of ahead of time by selecting those concerns when booking your ticket.
Use sites like Tripadvisor, Consumerreviews.com, and airlineratings.com for user reviews of comfort, food, and hospitality.
One last tip...BOOK DIRECTLY WITH YOUR AIRLINE IF YOU WANT TO CHOOSE YOUR SEATS
This many not be something you have thought of, but it's a lesson many people learn the hard way. Many international airlines do not allow you to choose your own seats if you book through a third party website. EVA Airlines is a good example of this. We flew EVA Airlines through Taiwan to Indonesia. These flights are NO JOKE from Los Angeles. You're talking about a 13 hour flight to Taipei, Taiwan, then 5 more hours to Bali, Indonesia. You want comfort, and if you can't choose your seats, everyone else will, and you will likely be put in the back rows. Problems?
My advice? Book directly with the airline once you have located a good price on a third party website, and choose your seats right away! An excellent resource for this choice? SeatGuru. This website allows you to see reviews of SPECIFIC SEATS on the style of airplane you are taking. Simply look at the flight information for the aircraft style, Google, and VOILA!