One thing in advance: Sure, there are several websites that give advice on how to fly cheaply. Most often they propose things like "fly on a wednesday rather than during the weekend" or "do not fly in the main travel season". But what if you simply can`t choose when to fly freely and must do it during the peak times? There still are some tips you can follow to make sure you don`t pay extraterrestrial high prices:
The first step is to compare prices. And yes, it is annoying at some point, but there is simply no better way to find a cheap price. Check comparison websites like skyscanner as well as the direct web pages of the flying companies as they sometimes even offer some better deals.
Also, try different airports. Obviously, sometimes you have only one option for an airport, but especially in your home country you know all the airport options around you. Trying different airports can not only have an impact on the price but also the available flight dates/times.
One more thing to actually do in advance is looking on the internet for cheap airlines in the region you are travelling to. This can actually double your chances to find less expensive flights.
One more point is to try and fly with hand luggage only. On shorter city trips and when going to warmer countries this should actually be relatively easy, even if you are not a complete minimalist. Most airlines allow a small suitcase and some "personal item" which is pretty much a not too big backpack or crossbody. In there you can easily fit a number of outfits, travel sized toiletries, a towel and some snacks. Not having to pay for check in luggage usually saves you quite a bit of money, on the very short flights even half of the price.
In case you simply have too much because you are going on a longer trip or into a clod climate, you might want to consider sharing one big suitcase, meaning that one of you books one suitcase and you both pack into it and share the cost as well.
Futhermore, don`t pay for any extras like choosing your seat in advance or food on the plane. In terms of food, simply bring your own. You are allowed to take pretty much everything through security, which is great to avoid the ridiculously high airport prices. And when talking about the seats, simply wait until you get or can choose one when you do your online check in. In case you don`t get some next to each other, simply ask a person to change with you on the plane. Mostly you find someone who does it on the first try.
As you see, there are plenty of things that can save you a few dollars. Still, you need to put a bit of effort into your search to be rewarded with the perfect flight for you. So go online, start searching and get on your next plane!