Need to book trains during August 2012

Dear Sir,
We are travelling, two persons, between neuchatel, montreaux, lauterbrunnen and then onto munich via zurich.
Is it necessary for us to reserve seats with our eurail pass during busy summer months such as August.
We are planning to buy the Jungfrau centennary 3 day pass is it necessary to reserve seats on the jungfrau train system during our time there.

Visser
It is not possible or necessary to reserve seats in Switzerland including the Jungfrau pass trains except:
-If you have a 1st class pass you can reserve VIP seats on the Golden Panoramic Express
-You can reserve seats from Munich to Zurich. I would not unless you are travelling on a Weekend. Make sure your pass includes Austria or you will have to pay extra on the train.

Dick