I kept a note on my phone every time I booked something this year, with the price, the date I booked, and how I felt about it afterwards. Twelve months of that is enough to see which of the folklore is real.

Short version: two things save real money and everything else is noise dressed up as strategy.

The two things

Being flexible about the day. Not the destination, not the month, just the day. Shifting a departure by forty eight hours in either direction changed the price more than anything else I tried, repeatedly, on almost every route. Tuesday and Wednesday departures were cheaper more often than not, but the pattern isn’t reliable enough to plan around. Just look at the whole month grid and pick the low one.