We were in the Cinque Terre for 4 days and got the 3-day pass for 41 euros. We arrived by train, and we purchased our passes to walk/hike the Cinque Terre trails at the La Spezia railway station. You may purchase passes at every station stop. Train times are listed at the stations and you receive a timetable with your pass. We also received a map of the trails and they mark the ones under construction.
If you do not purchase the pass, it is a couple euros per ride on the train. Check about validating your train ticket before the ride. You could pay a fine for not following the train rules. They take no excuses, only fine money. We saw it happen.
