Swiss pass - do i need to buy tickets in advance?

Hi. i have a swiss pass and am finding booking trains a little confusing.
i know the site says you SOMETIMES need to buy tickets in advance but i don't know if i need to. the timetable keeps insisting i put in a return journey date but i only want 1 way and can't seem to find that option. so therefore i can't check if i need to pre-book the tickets or not.

Basically, i want to know if i need to buy tickets in advance for the following journeys. if i do, how do i go about doing this?

if i don't need to, do i just rock up at the train station on the day and hop on??

i plan to go:
zurich to lucerne
lucerne to interlaken
interlaken to bern
bern to geneva

thanks.

also, while i'm here, what is the best way to organise tickets for the Mt titlus cable car and the jungfra top of europe tours? better to just book there on the day? any idea how much extra i will need to pay?

thanks so much for the help - the answer i got to my previous questions was really helpful - great site!! :-)

yep, this is the timetabl ei used and i must be really blind cos i can't see where it says single trip and it keeps asking me for return dates. but if i don't need to worry about pre-booking then it doesn't matter. thanks!

Contact the Swiss Tourist Board they were very helpful when I decided to go by train instead of hiring a car after flying to Geneva.
A word of warning, have the different platform numbers you will need written down as I was sent from one platform to another by Railway employees as I did'nt do the job properly and they were no help at all.On my return journey I knew exactly where I needed to be and the times of the connecting trains,which made the journey home far less stressful.

just a word of advice re junfraujoch,if the weather is bad and you have purchased tickets i think they only valid for that day..so go to interlaken, if u can , wait for a good clear day, then book at the station in interlaken..like wise for places like neisen,neiderhorn and to a great respect piz gloria..or schilthorn...a cloudy day is a waste of money, as you see absolutly nothing..
rob

any couples staying in interlaken from june 17th wish to meet up please contact me . rob