To get there take/leave La Paz from the Cemetary area - passage Bs13. There are buses leaving every hour until 3pm.
You can also bypass La Paz if going to/from Copacabana. Get on a La Paz bound bus/minibus/micro from either town, tell the driver you wish to go to Sorata/Copacabana and you will be dropped off at the small lakeside town of Huarina (2 hours from La Paz). Cross the road and wait for a Sorata/Copacabana bound bus with space to pass. They should honk their horn if they have space and see people waiting, but it wouldn't hurt to keep an eye out and flag one down if you see it first. Best to get started early as you may have a bit of a wait at Huarina - it should still be quicker than going all the way to La Paz then 2 hours back in the same direction though.
Buses arrive/depart Sorata from the main square.
Taxis are available, although the town is tiny so you will only want one for an excursion or perhaps if staying at Las Piedras (it's down a very steep hill, we elected not to lug our backpacks back up it!) or Altai Oasis (on the way to the caves, about 45 minutes walk from the main plaza). Your accommodation should be able to call one for you.
Hike to San Pedro caves, around 2 1/2 hours each way from town. Stop on the way or way back at Cafe Illampu or Altai Oasis for drinks and food. Swimming is possible in the caves.
Other than that, just relax and admire the beautiful views! It's a nice antidote from frenetic La Paz.
Small Sunday market, mostly selling food and general goods. Good fruit and vegetable market every day.
Sorata is not the place for a wild night out! Casa Reggae (see below) has a bar with beer and cocktails available.