Tickets (Biglietti) are relatively straightforward to secure. Most clubs employ a third party to administer ticket sales and each club usually has a link to that third party site. The main ticket sellers being Vivaticket.it, Ticketone.it and to a lesser extent Etes.it.
If you are planning a trip its difficult to predict the kick off times or dates for Serie A and Serie B games until the TV schedule has been coordinated which tends to take place between 4 and 6 weeks before the games are due to take place. For this reason, and wanting to secure good prices on flights and accomocation, we select a city where we will be within easy reach of several possible games across the leagues and then choose the fixtures to go to once the TV schedule is confirmed. Milan and Bologna are good bases with plenty of teams within an hours train ride across all divisions.
For the bigger teams, the clubs own supporters get first chance to buy and then the sales generally open up to general sale. The timing of this can vary from say 3 weeks for the San Siro, to a day before in the case of Venzia but the norm is about a week before the game. We have never failed to get tickets to a game although Sassuolo v Juventus was a close call and an email to the club secretary sorted us out in a more manual fashion. Shame the game was 'the stinker of Sassuolo.'
When booking tickets on the ticket sites mentioned previously, they will of course be in the Italian language. They do have an English langage selection but it doesnt always translate into all the details you have to select and complete. Italian fans are subject to strict conditions and have to register with a club and their home region but for foreign fans you will need to select a) Foreign in the drop down of all the Italian regions - at the bottom of that list is 'Foreign' and b) Regno Unito = UK. You will need to complete name, address, DOB, passport number among the personal details required. Tickets will then be emailed to you immediately and can be downloaded to your phone or printed off.
Take your photo ID to the game. You wont get in without it.