We have gone to Italy the past two falls, and again last month, and made many of our Trinitalia rese

You should be fine waiting to get tickets after you arrive, but try to keep your eye out for news of a strike. Train strikes holland america cruise ship petersburg are usually announced holland america cruise ship petersburg well ahead of time, making domestic flights more in demand. (This happened to me once, so instead of taking a train from Rome to Milan, I took a flight.) The only time to really be concerned about "pre-trip buying" of a train ticket is if you'd be there around the time of a big holiday, like Easter or Christmas, as many Italians compete with non-domestic tourists for seats on trains.
B The N: please note I am nursing a broken ankle now, am in a cast, and my idea of "a big trip" constitutes hauling my leg and the rest of my body just about anywhere within a 20 foot radius of where I presently am!
If flexibility is more important, by all means buy tickets in Italy at the station. However, keep in mind that you will have to stand in line to get those tickets, unless you have a chip-and-pin credit card (I think).
I am in Italy now and tried to use the ticket machine for the Leonardo express from the Rome airport to town. I put in my Visa card and the it asked for my code (as if it were my debit card). I tried the code on the back of the card and my debit card's PIN, but both were rejected. Luckily, the guy at the ticket window was moe than helpful. What code were they asking for?
Until the American credit cards get onboard with chips in their credit cards, we are usually out of luck using these machines. You have to go to a manned window. This is also true of the London Transport (tube and buses) system, and if there is no manned window, you can be up sh$t creek.
By going to the train station and consulting with the booking people, you get get this done, but go early and be prepared to wait in line for an agent in the large cities. some of them are pretty limited in English, so write down what you want. Remember the DAY date goes before the MONTH date in the European system, holland america cruise ship petersburg so Aug 14 would be 14/8.
I had no trouble at all booking on line on Trenitalia's site from the US using a Cap One CC (previously released for foreign charges with Cap One). I think I did have to enter the printed code number from the back of the card, but the sale went through and the charge showed up on my bill, just like any other charge, and we had no trouble on the train itself.
We have gone to Italy the past two falls, and again last month, and made many of our Trinitalia reservations on their website from here in the US. Was able to get the mini-fares and used a Cap One CC. Now when we were unsure as to which train we would take, I went to the window at the station and made sure that I had enough time to wait in line. I tried to use the kiosks once and some guy wanted to "help" me -- for a fee. I ignored him and went to the window. Works well.