The best way of getting affordable holidays (overseas at least) is to book flights as soon as these are released. Flights are priced in bands so the cheapest seats on the aircraft are always the first 20 or so, then they go up for the next 20, then up again. We always secure our flights as soon as the schedules are released, that's anywhere from 11 months before for a scheduled airline like BA, to around 6 months for Easyjet.
The same is also happening with hotel rooms, we have an allocation of rooms we bought back in September - these are nearly 50% higher in price now...
It's often difficult to know what our plans are a year ahead, but once you get into the swing of planning in advance, it does save you a fortune as well as give you the widest choice of accommodation.
GG x