Visiting any of the destinations above. There's enough material on the web nowadays to help you decide and discern.
actually knows
Cycling around San Pedro. Follow the guidelines above to get an idea of the places you can expect to reach. Other destinations, such as Piedra de la Coca, Catarpe, Garganta del Diablo, and Quebrada de Tambores can be accessed only on a bicycle or rented car, as they're not part of the regular tours. If you're planning to go there, then, by all means, purchase the only thorough map of the area, courtesy of the Technische Universität Dresden. It can be found at many souvenir shops and currency exchanges. Otherwise, bring a GPS, or hire a local guide who actually knows what he/she's talking about. Turismo Tekara across from Toconao 500 rents good quality bikes for $4000 pesos for a half day. Pick it up the night before, leave early before it gets hot and return it in the afternoon. Bring lots of water. Biking on the dirt roads here is safe, cars drive slowly past you, and the scenery is stunning. Be prepared to bike hard and get out of the sun before late afternoon.
Horseriding in the area. There's plenty of agencies that offer this service; La Herradura is one of the best. While riding on horseback is not the fastest way to travel, it can be one of the most fun. One you shouldn't miss is the Moon Valley-the horse track around it will take you to places unaccessible to other kinds of tourism, and has enough thrill to send you home satisfied! If you've done the usual circuit, and are ready for some more, then take it in the morning. Watching the sunrise between salt-ridges is a unique experience.
completely biased
Be sure to check out the book of complaints in the tourist office on the plaza before handing over cash to a travel agent. While not perfectly accurate, it is especially helpful to choose an agency to travel to Uyuni, Bolivia. As for the ones in San Pedro, standards can vary widely; the best agency of yesterday might be in tatters today, while the best one of tomorrow could give only mediocre service today. Maybe you think of doing some research of your own-if so, then completely disregard travel books, and ask at least five locals; unfortunately or not, most of them are completely biased. This applies to hotels as well. Be extremely wary of tourist guides giving advice, especially if you're female-they're much too well-known for trying to convince visitors to pick this-or-that agency, in the knowledge that they'll see the same visitors aboard the van the next day.