Probably cheapest to buy well in advance Paris>Interlaken and Interlaken>Venice from national rail sites. See http://www.eurotrip…. for those. However, you will not have any flexibility if you buy the (cheapest) tickets in advance.

For Interlaken to Venice, I suggest you look up the possible train routes and check for delays and change of trains, and of course cost (a sleeper has a higher cost). Its not uncommon that you will find you have to change trains once or twice, and spend some hours in delays even when you aren’t changing trains. You find few routes where you get on a train after dinner and get off early in the morning at your destination, sleeping all the way.

Also, there is a lot of great scenery on this route; I would rather see it during the day than sleep through it or try to see it in the dark.

How are you traveling for the rest of your trip? These two will probably be expensive unless you book well in advance. A Eurrail pass, if you can also use it on other parts or your trip, may save you quite a bit.

Thanks everyone for the tips. Well everything before Rome will be either bus or train, and from Rome to the remaining part of the trip will be by air. And i want to book everything with in the next 2 weeks.

A railpass may save money for this trip if you aren’t willing or able to book all of the tickets on-line in advance from the individual national rail company websites. Try using railsaver.com — either in the trip planner or under the “bookings” tab.