I'm planning to go from Athens to Delphi and stay one night. Then head north to Meteora/Kalambaka and stay two nights. I've been reading it's not so easy to do this. Some say it's easier to go back to Athens after Delphi and then go to Meteora from there. However, prior to that I will be going to Nafplio, Mycenae and Epidavros and then going back to Athens. I'll be going back to Athens again after the Cyclades. That's a lot of backtracking. What is the easiest way?
There is no easy way. It would involve going half-way back and waiting for a bus connection in somewhere like Thives ... but because busses are not set up for quick-tour efficiency but instead for the need of Greek townspeople (mainly to get to Athens and back), you might even have to stay overnight somewhere. I believe there is now a day-excursion by train to Meteora. My answer would be to get a really good video of Meteora, and then spend the time saved in the Argolid area.
I booked a two day/one night tour of Meteora via VisitMeteora from Athens. The train connection to Meteora was easy.