Poland and Pol Rail

Don't waste your money using a booking agents. The 60PLN fare is for Pospieszny
(fast) trains, just appear at the ticket window at the station about 30 mins or so before the train goes (there may be a bit of a queue[line}). These tickets are good for any Pospieszny or Osobowy (slow} trains, as long as you stay within the route and time frames stated on the ticket.
A 2nd class Pospieszny ticket allows you to sit in 1st class on an osbowy train if it's there, however you're better to stick to the fast trains.
If I can be of help drop me a PM,

There are sold out trains, usually weekends or holidays. But usually there is space the day before. Also some queues are really long and one half hour is too short.

{quote:title= Irishtaxidriver wrote:}{quote}
These tickets are good for any Pospieszny or Osobowy (slow} trains

That's not true anymore, since December 08 pospieszny tickets are no longer valid for osobowy trains.

Re OP's question:
Most of the trains on that route are pospieszny trains. Places on these trains cannot be booked, the ticket is sold for the route only (Szczecin - Kraków via Poznań for example) and you can use any pospieszny train you want within the ticket's 2-day validity period, stopovers are allowed. You're never guaranteed a seat on those trains - but as you'll be travelling in March, trains won't be full.

There's also one train with bookable seats (TLK) between Szczecin and Kraków. In March I wouldn't bother with advance booking, but if you really want to book, you can do it on-line via PKP Intercity website [https://bilet.intercity.pl/irez/] and print your ticket yourself, instead of using the rip-off Polrail site.

#2 Only trains with Szczecin reservations can be sold out (Ec/Ic/Ex/Tlk), these are more expensive than Pospieszny, not sure about Szczecin but some stations have another booking office in a different part of the building from the main ticket windows (Katowice for example), they usually have shorter queues.

#2 Only trains with reservations can be sold out (Ec/Ic/Ex/Tlk), these are more expensive than Pospieszny, not sure about Szczecin but some stations have another booking office in a different part of the building from the main ticket windows (Katowice for example), they usually have shorter queues. Thanks for the information about the new rule Igor, that'ill save be from being fined (again! ) for not having a valid ticket

Igor and Irishtaxidriver make a good point on the Pospieszny.
There is another ticket office, near the end of the pedestrian bridge above the tracks. This is on the short way to walk to Aleja 3 Maja, and Hotelik Elka-Sen.