Sorata is a town in Bolivia, about a 150 km northwest of La Paz. It attracts mainly folks that plan on hiking or climbing the mountains around.
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.