Set aside money for your trip. Tickets from Interlaken to Paris will cost between $125 and $250 depending on what class ticket you buy. Second-class travel is more affordable and is fairly comfortable for shorter trips. First-class travel typically includes more comfortable seats, hot meals and more attentive service.
Look into or book a Eurail France-Switzerland Pass, as it will save you money if you plan to travel between Interlaken and Paris on multiple occasions. This will afford you added flexibility if you travel by train through France after you arrive. Passes enable you to travel for free on France's national railway during your entire trip.
Book a 'Flexi' ticket, which is advantageous is you desire flexibility in your travel plans. It is easier to make changes in your train travel when you book a Flexi ticket. It costs between $50 and $100 more but is worth it if you have not totally cemented your plans or anticipate adjustments.
Take advantage of discounts. Follow the link on the Rail Europe home page for 'Group travel,' which will help save you money even if you are only traveling with one other person. The discounts really kick in for groups of 10 or more. There are also specials for seniors and young adults under 26.
Allow for the trip between Interlaken and Paris to take between 7 and 8 hours, which means you might want to think about first-class travel. Stopovers are very brief, sometimes only 10 minutes in total. Your train will go through Basel on your way to Paris. The second leg is much longer than the first.
