I've gotten some good fares, but worry that I might have done better. If I try to arrange any fare that is even slightly complicated, I go to the airline or a travel agent. Silver Spring, Md. I've subscribed to Fare-Tracker for ages, but I've never once EVER been able to get anywhere close to the price of the advertised low fare once I actually try to book it. Actually, it's the yield management computers that are your enemy.
Fares can change several times a day, depending on the flow of reservations.
My best advice is to move fast once you see a low fare. Sometimes it's best to get on the phone and make a pest of yourself with an airline ticket agent. The real Amtrak swamp is in a Congress that wants trains running through every district, but doesn't want to pay for it. It is a fiction to believe that Amtrak will ever pay for itself. No national passenger system does that anywhere in the world, no matter what fantastic claims some people make.