If you plan to travel using Swiss trains (and I would recommend this) then you could consider buying something called a 'halb-tax' before you purchase any tickets.
It costs around 200chf (that might be a year or so out of date) but once you have it you can purchase train tickets - first or second class - at half price.
So, for example, a trip from Zurich to Milan in first-class would drop from around 300 to 150 chf.
So, if you plan to travel, say, more than three times it pays for itself. I have another tip of a similar nature: Swiss trains are a lot cleaner, newer and better serviced than Italian ones, so if you are travelling from Switzerland to Italy (which is a great journey) then either ask at the ticket counter who is the operator, try to get 'SBB' trains (the Swiss ones) rather than TrenItalia.
Another good operator is CISAlpino which I believe is some kind of joint operation.
Actually, on a trip from Zurich to Milan, the Swiss "halbtax" discount of 50% applies only to the Swiss leg of the journey (namely, Zurich to Chiasso). From Chiasso to Milan, the fare is full price. One can get a 25% discount on Italian journeys by buying another discount card, this time for the FS (Italian railways).
The Halbtax for a year is only really available for residents (anyone with a CH address). For tourists, the one month variant for 99 CHF is probably better anyway:
For tourists who want to use the railway often I recommend the "Swiss Half Fare Card". It costs chf. 110. It lasts one month. You can buy half price tickets for railway, bus, boat. You can get a free "Family Card" with the "Half Fare Card". With the "Family Card" children from 6-15 years travel for free if they travel with their parents. You get the "Swiss Half Fare Card" at the Railway Stations.
You'll need a passport photograph and the card will be sent to you within a few days, however you'll get a receipt that enables you to get the 50% discount straightaway.
The Halbtax is also valid on trams and buses in most cities. Furthermore, you'll get a 25% disount on rail travel in Germany and Austria when buying your ticket in Switzerland.