Is it required to book the cable car to Mt titilis and tour to jungfrau in advance?

No. Actually you cannot book except Jungfrau trains when you are a party of more than 10 persons.

No - and you don;t want to do it. If the weather is bad the tops of the mountains will be in the clouds and you will see nothing from the top - so there is no reason to ascend. We had to wait 2 days and ascend the Jungfrau on the third - since it was socked in the first too - althouhg the valleys were perfectly sunny - form about 6,000 feet up was clouds.

Ditto to nytraveler since you can't predict the weather or other unforeseen events. I never book anything in advance if it's not necessary.

Nytraveler, if the valley were perfectly sunny, how do you know the condition on the top? It there any way to find out?
Say, we are staying in Lauterbrunnen, and we wake up in the morning, and it looks sunny - how do we know if it is cloudy at elevated levels?

They can tell you at the train station. Or use the internet webcam to see for yourself:

http://www.swisspanorama.com/html/jungfraucam1.html

Hi helen,

On the day I went from Grindelwald I could see the top of the Jungfrau and it was crystal clear. I also checked the forecast to make sure it would stay that way.

Yes, you call the train stations and they tell you conditions at the top of the mountains (we don't take a laptop on vacation).

Got it! Thank you, guys!

Thanks for the info -- I'm going there also in June.

Does the Swiss Pass cover Jungfrau trains (any discounts or included)? I'm thinking about buying a Swiss Pass for 8 days upon my arrival in Zurich on June 1st.