@ Badass: It is definitely still Listicket, since they took care of the season tickets as well.
Now, depending on the opponent, Listicket may or may not sell ticktes online. For the big, high risk games (Inter, Roma, etc), they will most likely NOT sell tickets online anymore. New rule that is in effect since last season. In those cases Listicket is still the agency that sells them, but only in the shops (and possibly by phone.) See the links Boksic posted, enough possibilities.
Since you're planning to go to the Parma game, you can be pretty certain that there will be tickets for sale on the website because that's one of the least risky games of the entire season. In your case, I'd keep an eye on the exact date & hour of the sales start (mentioned on the Juve site) and make sure that you're online at that time. Pretty good chance that you'll have your tickets.
You'll have to collect them at the stadium, probably starting from 2 hours before the game. When you order through the Listicket website, you should receive an email with the exact address, since this will depend on which sector you bought tickets for. If you don't receive such an email, you can look it up on the listicket website yourself as well.
I'd advise against unofficial websites (Seatwave & whatnot), they'll charge 3 or 4 times the normal price.