When to book train tickets?

Put the Italian city names into the trenitalia website ( https://www.trenitalia.com/en.html ) and pick the one that fits your schedule and budget the best. Note the restrictions on the discounted fares, but you can save a pretty penny by buying in advance! The July tickets are in the "after June train ticket/schedule release" so they probably aren't up yet or able to be purchased. You take the routes that are offered on the website, as you have already mapped out your route with the order of the towns you are going in. Others will probably have more specific logistical information (especially about ferries and the like on Lago di Como).

Hello italytravels2024, and welcome to the forum!

You'll want to take the fast trains between big cities - like Venice to Milan - these come with assigned seats on a specific train. The earlier you buy the cheaper the tickets but you're trading economy for flexibility. Since you're not taking a fast train the same day you're flying you should be able to decide when you want to fly and pre-buy your tickets if you want to.

The state train company is Trenitalia - they run fast trains and local ones. https://www.trenitalia.com/en.html
.Italo is a private company that only runs fast trains. The service between the two is pretty similar. https://www.italotreno.it/en

Local trains called regionale tickets are always the same price - just buy them when you need them. This includes the train from Milan to Como/Varenna which is not a fast train.

Download the Trenitalia app to check schedules, buy tickets, validate them for travel and track trains in real time.

Really good general train information here: https://www.seat61.com/train-travel-in-italy.htm

Have a great trip!
=Tod