Booking Trains in Advance in Northern Italy

For any "highspeed" trains (i.e. Frecciarossa), you'll want to book those in advance as soon as possible. That's because those trains have assigned seats and various fare classes (kind of like airplanes), and there are only so many available for purchase. If you buy sooner, you'll have access to the cheaper tickets, versus when you wait until the last minute, the train seats could be sold out or more expensive. For regional trains (I think of these like local, commuter trains), the price is set by the time and date. You can just buy those the day of your trip.

For the Venice to Milan, I'd definitely go ahead and buy now. The other ones I think are regional trains and you can buy in the station right before your train.

If you'll have service on your phone while you're there, I highly recommend the TrenItalia app. So easy to buy tickets straight from your phone and avoid ticket lines. We've been able to show up to the station, buy tickets on my phone, and go right to the train. It saves so much time. Have fun on your trip!

The above post may be a little misleading imho. There are only so many DISCOUNTED TICKETS available for purchase. Full price tickets, called BASE on trenitalia.com and Flexi on italotreno.it , rarely sell out. The chances are close to zero on a route served by two competing companies like the Milan-Venice.

On the other hand, if you'll always find a seat at the top price, the difference with the discounted fares is quite noticeable.

For instance I entered August 22 as day of travel on trenitalia.com A BASE fare ticket in standard class from Venice to Milan at 10:48 AM costs 49 Euro per person. An Economy fare ticket on the same train costs 36,90 Euro. The cheapest fare is called SuperEconomy and it costs Euro 33,90 per person.

Less expensive means more restrictions regarding changes and refunds. Get a discounted ticket only when your plans are set.

You can do the same check on italotreno.it, the private competing company that runs only high speed trains on major routes.

The price of regional trains is set, there are no discounts for advance purchases. More, there are no reserved seats on Regionale trains, so they can't sell out. The benefit of getting Regionale tickets online is that you can freely get on the train without having to time-stamp your tickets.

There is also a "Me & You" fare for couples traveling. These are generally less expensive fares as well. I paid €59 for the two of us Milan>Venice in mid-September.

Your other journeys are all on regional trains (at least the viable options), so no real issue on getting a seat. What I do recommend is that you be flexible on departure times. While there may be a train every hour, some of these have multiple changes and/or take an additional hour plus in travel time.