To start with, I will concentrate on websites where to look for flights and then you will have some good tips from other blogs and articles that can get you inspired.
1. Skyscanner
Is top meta-search website. Still you may get good deals on http://www.flugladen.de beware that depending on the payment method, there is an additional 25-30Eur commission. If you get a good deal, could be woth paying the extra fee. Flugladen is also a platform recommented by UrlaubsPiraten.
2. Swoodoo powered by Kayak is also an excellent version.
From this meta search, you will be getting other booking portals like Kayak or Lastminute. What stood out as best priced was http://www.checkfelix.com
3. Momondo company with base in the Nordic countries
Displays competitive prices from different providers just as the two above mentioned companies.
If you check these 3 display booking websites, you will for sure get the cheapest flight from the internet. Beware of the commissions to be paid when you are redirected to another booking platform, as they are just the middle man for agencies that actually have the flights.
To check different airport to fly from, I suggest: Skypicker
Also, I would like to share insights with you like the following article found on Business Insider: "23 Secrets To Booking Cheap Flights"
Wiki How with 'Get cheap Flights' is a complete guide regarding timing when to book, where to look for flights and other tips.
Nomadicmatt offer the following warning: '
Remember Not All Search Engines are Equal
When we doing a Web search for airline tickets, we may search Expedia or Orbitz. As this article shows, you are making a big mistake if you do just that. These sites either work with or are owned by the airline companies and don’t offer unbiased fares. You need to search as many flight search websites as you can in order to ensure you are leaving no stone unturned.'I would be happy to know if you found any other alternative for cheap flights when using the internet.