Swiss Travel Pass

How far on advance? How much time do you need? You can buy it when you arrive at any train station. If arriving by train from elsewhere, and you want to use it on your arriving train, you can buy in advance on-line, specifying the date you want the validity to start.

You don't need to "book" trains, you just board and show the conductor your pass. If it is a flex pass, have the use date filled in in ink before boarding. The only trains needing reservations are Glacier Express and Bernina Express.

The Swiss Travel Pass is sold up to 6 months in advance of your predicted travel date and is pre-validated for the consecutive travel period you request or for the one-month travel window of a flexi pass. See lots of info on that link. Most Swiss trains don't need reservations, but if you want to book panorama seats of the Golden Pass, Bernina Express, or Glacier Express, then one way to do that is directly through their separate web sites, possibly not more than 3 months ahead, but you could try further out if you're ready to commit.

Details on the Swiss Pass options, and purchasing are on the SBB (Swiss Federal Railways) website here: https://www.sbb.ch/en/leisure-holidays/travel-in-switzerland/international-guests/swiss-travel-pass.html

How far in advance can you buy the STP?

I am not sure, but there is no incentive for buying in advance. It is always the same price (in Swiss Franks). You can either buy on the SBB website (in which case you get a print-at-home ticket), or at a border or airport railway station. All at the same price.

So once I buy the STP how do I use it?

Duh, you get on a train ☺. It is that simple. Makes sure you have your Pass and your ID (passport) with you and get on any train, boat or bus. When the ticket inspector comes round, show them your pass and your passport.
If you have a Flex pass where you fill in the dates you want, you have to do this before getting on the train.
This map shows where the pass is valid, which is all trains, buses, boats and city transport apart from a few mountain railways, where you get a discount: https://www.sbb.ch/content/dam/infrastruktur/trafimage/karten/karte-sts-pass-gueltigkeit.pdf

How far in advance can you book seats on the trains?

You don't. You do not need to reserve seats on Swiss trains, and it is usually not possible. The exception is the four named extra tourist trains (Glacier Express, Bernini Express, Golden Pass Express and Tell Express), which do need reservations.

The Tell Express, or Wilhelm (William) Tell Express has recently been renamed as "Gotthard Panorama Express." In addition to train carriages with panorama windows, it has a photo coach with windows that open. The advertised route still includes the boat on Lake Lucerne.
Here are informative websites about it:

https://www.sbb.ch/en/leisure-holidays/travel-in-switzerland/panoramareisen/gotthard-panorama-express.html?tracking-marketingurl=gotthard-panorama-express

https://www.myswitzerland.com/en-us/gotthard-panorama-express.html

https://www.sbb.ch/en/leisure-holidays/ideas/offer.html/zuege/gotthard-panorama-express

LindaL

Looks like a beautiful trip. I browsed at the links and it says you can do a day trip but there are not much detail.
Can you use the STP?

Thank you,

You can use an STP. There is seat reservation/supplement fee of 24 CHF for the whole route which is not covered by the STP.

I've taken this route many times, but without the special panorama train carriages. So, I didn't need to pay for any reservations, and the Swiss Travel Pass covered the whole trip completely. I loved the part on the ship on beautiful Lake Lucerne, which travels from Luzern to Flüelen. But the train ride scenery on the way to Lugano was not one of my favorites. I do love Lugano, with its old town cobblestone streets and the flowered promenade along Lake Lugano. I take a lake ship to get to nearby San Salvatore mountain, which looks like it popped out of the lake, and the nearby ancient village of Gandria -- all covered with the Swiss Travel Pass. As far as I'm concerned, I'm grateful for the new Gotthard tunnel which gets me to Lugano and back quicker than when I had to take the longer way through the old shorter tunnel, and the new tunnel route still comes out of the tunnel in time to see some of the Ticino area. Funny story: One Saturday, last July, it seemed like all of Switzerland had had several days of dark, rainy weather, but this day, at least the Ticino area had a promising weather forecast. We rode the train quietly, which was packed with local Swiss people going to Ticino for a weekend outing. When we finally got out of the long Gotthard Basis tunnel, the sun shone into the train; we all saw the bright blue sky, and the whole train car applauded!

I do the Lake Lucerne part by ship one way from Luzern, and then take the train back to Luzern, as one day trip. For the Lugano part, I take the train from Luzern all the way to Lugano, which saves me 2 hours each way than if I'd used the ship. That way I have time to explore the Lugano area as a day trip and get back to Luzern the same day.

It would take too long to make the whole round trip, including the ship, as a day-trip.