train from Roma Termini to Florence SMN

In Italy, platforms are often not announced until 20 or 30 minutes before the departure of the train, so you have to check the schedule board for imminent departures, similar to checking your gate at an airport. See more at http://www.ricksteves.com/travel-tips/transportation/trains/getting-on-the-right-train.

The platform is normally listed on the departure boards approximately 15-20 minutes before departure.
See the photo here, look for the column marked "Binario".

For more info and photos on train travel, see roninrome.com. Tons of helpful advice, including different types of coffee.

Thank you Laura, Chris and Zoe for the info...Helps a lot......

You can also checkout the site the man in seat 61 with some good information in trains, stations with pictures.

http://www.seat61.com/Italy-trains.htm

Actually all trains have pre-assigned tracks, throughout the year. However it's a good policy to check the general electronic board, because they are often subject to change due to delays etc.
It's like airplanes. They may be assigned to dock at a specific gate, but if the previous plane is late and the gate is not available, then the Ground Control will operate a gate change.
The trains work similarly, they all have tracks assigned at each station, but track changes with trains are more frequent because trains have much more frequent arrivals or departures from the same track, compared to airplanes, which may make cause the Cabina di Controllo at the station to change those assignments. The Cabina di Controllo is the station equivalent of the Control tower at an airport.
To see the assigned track to a specific train, you must look at the paper timetable displayed at every track end. It looks like in the pictures below:
http://gabbianonews.tv/sites/gabbianonews.tv/files/field/image/orari_treni.jpg
http://www.cittadellaspezia.com/foto/2012/07/31/39755.jpg
http://thumbs.dreamstime.com/x/viaggio-del-giovane-leggente-l-orario-del-treno-nella-stazione-ferroviaria-40762083.jpg
http://www.stazionidelmondo.it/romaaurelia9.JPG

If the paper is yellow, it's the departures, if it's white, it's arrivals (this is valid throughout Europe)

A closer detail of the paper timetable looks like in the pictures below. The paper timetable gives all kind of info about the train (unlike the electronic one which just gives destination and time). One of the info it contains is also the "assigned track". However, as I said, that is subject to change, therefore it's a good idea to be on the lookout for the electronic timetable, because that's the only one that would display the last minute track change. However, if you arrive at the station early enough, it's a good idea to look at the paper table too, so that you get all kind of info about the train (and also the probable track number even before the electronic table displays it).

http://www.vitadapendolare.it/wp-content/uploads/2014/05/Tabella-orari-treni.jpg
http://www.miol.it/stagniweb/Foto6/avvi0134.jpg
http://imageshack.com/handle_redirect.php?ser=31&file=immagine059e.jpg

Another cool paper table to check at the station is the TABELLA COMPOSIZIONE TRENO (or train composition table). Below is an example from Germany (but it's available in all major stations in Italy as well, more or less the same way). That is a depiction of all cars composing the specific trains. It's good to check to have an idea how long is the train, where the first and second class cars are, and so on.

http://i1362.photobucket.com/albums/r700/guidobonati/20130830_185402_zpsac0fb5a7.jpg

The long distance high speed trains, no matter what station, are generally assigned to the center tracks, while the regionali are assigned to the extreme ends of the station. So for example I think Termini has 25-26 tracks. The frecciarossa to Florence is likely assigned to the mid tracks. Since the train out of Termini needs to turn left (north) toward Tiburtina and Florence, then it's likely to be on the center left tracks (probably 6 to 12 in Rome).

One thing to remember is that the timetable will show the FINAL destination of the train. So your train to Florence, will likely be destined to either Milan or Venezia or Torino. The final destination city is what is shown in the display, along with the train number and the scheduled departure time.
in your case your Frecciarossa 9566 is from Roma to Turin (Torino), therefore the display will show TORINO P.N.
http://www.e656.net/orario/treno/9566.html

(Does it show that I worked at Florence Santa Maria Novella station in youth?)