Start searching as early as possible
Airlines generally release tickets 11 months in advance. Once you know your destination start searching and continue to check at least once per week.
Flight prices are live and fluctuate constantly due to supply and demand, so have a price in mind YOU are comfortable paying and be ready to jump on it.
Sure, there are last-minute flight deals that might beat what you’ve already paid, but that’s not guaranteed. If you want to play the game of waiting for a bargain, you’re better off NOT having a fixed destination in mind.