The mountain has an eerie volcanic landscape, with solidified "rivers" of lava. It is used for skiing in winter, so be prepared for the cold at this altitude, even in summer. Even in good weather in summer, sometimes the top of the mountain is covered in cloud, especially during the afternoon, obscuring the wonderful views.
One bus a day runs to and from Catania to Rifugio Sapienza about 1400m below the summit on the south side, giving you enough time for a trip up the mountain and a wander. The bus leaves at 8.15 am from outside Catania train station. The bus stops at stop number 5 which is next to the area served by local buses, across the round about. Tickets for the bus are sold on board. The bus is a white coach with AST written down the side. The return bus leaves Rifugio Sapienza punctually at 4.30 pm - don't miss it, there are no other options to get down.
There are 2 ways to get around on Mount Etna:
1) From Rifugio Sapienza (Etna south), you can pay for a trip on a cable car/gondola lift and then a 4-wheel-drive vehicle. The round trip is 79€ per person (as of Feb 2017) but some close hotels have discount agreements.
The cable car/gondola lift runs from Rifugio Sapienza (1900m) to 2500m. It's 30€ per person, including return (Feb 2017). There is also a path just behind the cable car station if you want to walk. It takes around 2 hours to walk up from 1900m to 2500m. From the top of the cable car station you can then take a tour in a 4x4 (49€ as of Feb 2017), but if you are even moderately fit it is not worth it: The beautiful hike from the top of the cable car (2500m) to Torre del Filosofo (2920m), is fairly straightforward, and takes about an hour (~2.7km one way, 400m elevation gain). You can either follow the road, or more interestingly, there are some more direct paths.
Be prepared for some disinformation when asking about hiking options, especially when there is a conflict of interest in selling tours. The hike is moderate at most, you may be told it is steep or even dangerous. Not true. The hike between Rifugio and Torre Filosofo is a slog, but straightforward enough. Taking the cable car, the hike from the top of the cable car is little more than a walk, and kids as young as 4 were successfully doing it. Beyond Torre Sapienza (2920m) to hike up to the crater you will need a guide, available at the 2900m ranger station (25€ per person). The hike is an extra ~4 hours round trip.
Note: if you want to join a group from Torre del Filosofo to the crater, you should be at the ranger station before 11 in the morning. If you arrive later, there's a chance you won't find a guide.
Another good option is to get a guided tour with an electric mountain bike near the base of the cable car, which is 85 euros to the summit at 3,340m. They also have electric and non-electric mountain bikes for rent to explore the area.
2) From Piano Provenzana (Etna north) by walking to arrive on the summit Crater. This is a beautiful tour because it's possible to admire forests and lava sceneries.
The many Mini-shops along the side walks, the old fashioned houses and restaurants, and the locals that live there. There are lots of souvenir shops around Rifugio Sapienza.
There are several cafes / restaurants around Rifugio Sapienza.
The top of the cable car station also has food, with unsurprisingly high prices given the altitude (capuccino e3.5 panini e5).
You can buy many hot chocolates to warm up your bones. Also on colder months, as you go up Mt. Etna you will find several shops and there you can buy the drink, "Fuoco dell'Etna" which is a liqueur which will definitely keep you warm as you hike up. It will get very cold.