Need help with trains

the earlier you book, the better the price - normally. Esp if you want to go 1st class.

Seat61.com is the place to study and learn how to book your trains.

Go to OBB website for the Austrian trains. Book as soon as it's convenient. No reason not to.

For an overview of the trains available and costs, first go to www.TheTrainline.com

You’ll see that Railjet, (OBB) trains are usually the least expensive from Vienna to Salzburg (2.5 hours) and Salzburg to Innsbruck (2 hours). As luck would have it, you need to train to Innsbruck to get to Venice. So, overnight in Innsbruck’s beautiful Altstadt ( 1/2 mile from Innsbruck’s train station) and continue in the morning to Venice The private train company Italotreno often has the best deals from Innsbruck to Venice— a spectacular 5.5-hour route through the Austrian/Italian Alps’ Brenner Pass. Italotreno again has great fares from Venice to Milan (2.5 hrs.) if Trenitalia’s Frecce trains are less expensive, then book through Trenitalia.
You can get the best deals buying directly from the train companies’ own websites ASAP because, as of the moment, all your tix could be bought for less than €100 each. From now on, prices will rise
Have a great Trip!
For Railjet www.Oebb.at
www.Italitreno.com
www.Trenitalia.com

As noted above, use the OBB website for trains in Austria.

Use the Italian train websites for trains with Italian stations. The Trenitalia website requires using Italian place names (Venezia, Milano). Italo is the other rail line

https://www.trenitalia.com/en.html
https://www.italotreno.com/en

The Man in seat 61 is chock full of valuable info on how to use trains in Europe . Generally, for the long distance trains, discounts can be considerable when seats are booked in advance. But the cheapest come with restrictions on changes or cancellations, and are for a specific day and time.

https://www.seat61.com/

Don't forget to buy seat reservations in addition to the train tickets. In most cases they are not included by default.

For the salzburg to venice connection you might check the italian site as well. Might be a different price for the exact same train you find on OBB. For some reason for trains between Austria and Hungary the Hungarian national company sells the same seats on the same trains for less money. Same might hold true with the Austrian and the Italian. Dont know.

Thank you for all the suggestions! After looking at trip from Salzburg to Venice, I think we will stop in Innsbruck to stay overnight. The high speed train from Venice to Milan looks like the way to go. I will check the prices on both!