In Spanish, when do you use "volver" and "devolver"?

Answer 1

Volver is used when returning, such as "Vuelvo a casa," I'm returning home.  Devolver is used in returning an object to its original location, such as "Necesito devolver el libro a la biblioteca," I need to return the book to the library.  It is assumed that you collected it initially from the library, and that you are now in the process of returning it.

Answer 2

"Volver" means 'to go back' or 'to come back', whereas "devolver" is used for 'to give back' or 'to take back'. What makes it difficult for the English-speaking student of Spanish is that in English one uses the word 'return' to express the two different ideas. 

Answer 3

volver is intransitive (doesn't take a direct object). A person returns (him/herself). It is a synonym of "regresar."

devolver is transitive (takes a direct object). 

The good news is that they are conjugated the same way, so you get more mileage out of learning your verb endings, etc. and just need to add the prefix, "de"