S/O Duties
VFE at the risk of incoming from the vociferous minority here's the view from a CX LS driver
Turn up on time - for that, read early and properly rested
Be actively involved in the pre-flight planning - you are a full member of the crew and despite what some may think, your input IS valuable
Ensure the docs bag reaches the a/c with all the relevant paperwork and paraphernalia for the flight
Listen to the Capt's review of the maintenance log - again you are a full crew member
Usually, you will be expected to carry out the flight-deck safety/preparation check (Cb's, PA, Security, equipment etc)
Yes, it's expected that you'll prepare the bunks, although this is secondary to the operational pre-flight duties (some alternative initiatives are being explored such as getting the cleaning teams to make the bunks, but don't hold your breath)
During the start, departure, descent and arrival phases, active monitoring of the operation is required
During the cruise normally expect to assume PM duties - CFP, R/T comms and maintain situational awareness which includes anticipating actions for unexpected contingencies.
If you're in the seat with the Capt you have the opportunity to act as PF although this is clearly limited to managing the autopilot
Post flight - assist with tidying up the paperwork, charts etc and be responsible for ensuring the docs are returned to dispatch.
Return home and enjoy a long block of days off before repeating the process
I guess its not a particularly rewarding existence but if you can live with it on the rather abysmal terms being currently offered...