I will let this instructional video demonstrate the foundations:
There is a certain randomness involved in circuit bending. The nature of taking apart an object in order to produce new sound is intentionally chaotic, and the methods used are more trial and error than technical know-how. This leads to results that are often appropriately warped. It seems to me that the skill in circuit bending lies in the ability to map and utilize the sounds being produced.
It is interesting to learn that there is a spiritual aspect reflected within the circuit bending community. There is a general belief that the sound invoked comes from a connection to a parallel universe trapped within the circuits being tinkered with. The idea of harnessing the chaos involved and producing order by means of experimentation, allows followers of circuit bending philosophy the ability to unlock the hidden potential of their circuitry which isn't supposed to exist. As far as I can gather no dangerous cults have been established
I found this video online which I think demonstrates the vast array of what is capable with circuit bending, especially in regards to its application within electronic and synthesized music.