I get frequent flier miles almost exclusively from Delta because my American Express is tied to it and this makes me pay off my purchases immediately and plus when I buy delta tickets I get like triple points or something. I probably should pay closer attention to that :)
Anyway next Summer I will be taking my son on a trip. I have promised all my kids an international trip before they graduate from HS and his choice was Berlin. When I saw how close this was to Prague (and frankly since we live in Texas we consider a lot close...in fact we will be driving 4 hours to travel from a larger city to get better flight prices) I decided it needed to be a Berlin/Prague trip.
So basically my plan was to find tickets that were around $900 each. Flights to Eastern Europe are typically more expensive than say Paris or London. Unfortunately no matter where I looked I couldn't find anything less that $1100. Even driving to the bigger city where I would stay with a friend the night before we get on the plane.
So the flexibility plan works like this 2 cities + travel to another city to fly out of + frequent flyer possibilities = lots of time needed to come up with the best possible scenario.
I tried online sites like expedia and cheaptickets and while I found a couple of decent prices none of them fell in the $900 range. Plus it seemed to only be cost effective to fly in and out of the same city. This would mean on the way home we would have to ride a train BACK to the initial city hope on a plane and then drive 4 hours home. I wasn't looking forward to this in the least.
So I started looking at multiple city plane tickets. To my pleasant surprise not only was this extremely affordable, it saved time but it was flexible no matter which city came first. Plus i moved around some dates and found that travelling a month later would be better. AND it was so far in advance that when I looked up on my frequent flyer site I had more than enough miles to get a free ticket! So basically I found tickets with only one stopover with a multiple city ticket for $100 less PER TICKET than I was hoping for! A good day!
Basically, I know people say this all the time, but flexibility pays off!
Some things to think of:
Try a home airport that might be farther away but has more service. You are guaranteed to get cheaper tickets from there if for no other reason than because more carriers use that airport.
Be willing to change your dates. Originally I had one month in mind but things kept happening to push it back. The final month actually works out well because this means we will be in Berlin on my son's birthday. What a 17th birthday present! I bet he will never forget it!
Realize distance is relative. So if you want to travel to say Poland, I know flights are far more expensive than Berlin. but if you factor in a rail ticket and the ability to see multiple countries you would be shocked how much you save flying in to one country and taking the rail or renting a car to get to your final destination. Make sure you do your research though. I've had people travel to Texas and want to know if I could meet them in Dallas. This is 6 hours away. 3-4 hours is my max to drive without it consuming my whole day. So think about that and what you are willing to exchange for cost.
Days of the week matter. make sure you stay over a Saturday and try to avoid travels on the weekend (for a variety of reasons such as crowds and cost). I also think that the day you book matters too. I have heard that booking on Wednesdays is cheaper. I know that Delta gives deals on Wed. Find out if your preferred carrier does this too.
Hope these help and Good Luck!