Flying to Spain is definitely not cheap but adherence to a few principles can indeed reduce your air travel expenses.
You can work with various websites of airlines and travel agencies. Also subscribe to every a newsletter that you find fare on the Internet. Doing this will keep you updated about the air-fare, thereby reducing your legwork. Always mark your destination to be Madrid's Barajas Airport (MAD), every time when you search for airfares on travel agencies and airlines websites. Any other airport in Spain will cost you more and we will also put prices to twirl. This may even end your hope to find a cheap flight to Spain. According to most of the experts, Wednesday at midnight (EST) is time then most of the private airlines dump the unoccupied seats, so fortunately this can be a favorable time to go for air ticket hunting.
You may also travel by first reaching a major European airport outside Spain such as Frankfurt, London or Paris airport and then make an air travel using a cheap flight to screen. You can explore the options using bargain-basement airfare for Europe. From here you can use a budget European airline like RyanAir and it is being. If you book your tickets well in advance, you can avail a seat in no-frills European airline in exceptionally low prices. The only disadvantage in traveling like this is switching to a new airport. This will also include ground transit charges.
A budget airline will also be advantageous if your goal is some other cities than in the Spanish capital Madrid. Budget airlines also apply to secondary airports like Barcelona or Granada. This also saves on time and money. Because this method necessitates ground transits, it is only safe if you can accommodate layovers of several hours. This also has the advantage that you can spend some time in other European cities like Paris or London while you wait for your flight. This process is often called Trading Time in order to get cheap flights to reach Spain.
While you are using Internet and websites to book tickets, you can quote your price. Sometimes websites are really useful in getting great bargains if you exercise freedom to adjust your schedule.