The practices distinguishing Wicca from other religious traditions can be seen as special applications of something I am calling intentional consciousness. The difference I have in mind is between consciousness as the ordinary awareness of yourself and your surroundings and a directed or focused awareness in which you attempt to override the ordinary.

Another way of talking about this is to think of the Witch as seeking a deliberate dissociation--a temporary and usually only partial loss of the ordinary sense of self and surroundings in order to "become" another entity (what is meant by "possession" or "channeling") or to remain oneself in a seriously altered environment. Examples are the High Priestess becoming one with the Lady invoked through the Charge or the covener seeing herself in the sidh to witness the actions of the gods and goddesses of her chosen mythology.

Spelling as well as other acts of a practical magick are an effort to link your energies with a specific target, much as though you were programming a guided missile. Obviously this calls on you to think about your responsibility for anything you so will. This is where the classic rule holds: will what is evil and it will bounce back on you threefold.

Is it necessary to "believe" in order for your magick to be effective? If by belief in the conventional sense of saying that you accept things as really true, then you do not have to be a believer. Instead you can (and probably should) adopt an "as if" attitude, not too different from the attitude taken by an actor or a dancer who is really into her performance. The rest depends on the state of the web, and most of this is beyond your control. Be grateful when magick "works" (meaning that you get visible results), but do not be ungrateful if there is the appearance that it does not work.