Here is a short summary of two of the most common techniques that can be used for scrying.
Crystal gazing -- This is the method that first come to mind when the word "scrying" is mentioned. The crystal does not have to be large. The only requirement is that the stone that is being used must be very clear and as flawless as possible. It helps if you use a crystal associated with the Moon. Light the area with a single candle that does not actually reflect into the crystal.
Water gazing -- This method requires a large black or silver bowl.
The bowl is filled with pure water (rain water or water from a natural source if at all possible). Use a dish of water in a darkened room, lit from the sides by two candles. The dish should be a solid, neutral color. If you are lucky enough to live near a pond, lake or ocean, you can dispense with the bowl and just use the whole body of water as a huge scrying tool. (A quartz crsytal, or cluster of quartz crystals placed in the bottom of the bowl seems to enhances the energies.)
Fire gazing -- This method often provides startling results. The energy of the fire really lends something to the visions it produces. Anything from a candle flame to a bonfire can be used. All the usual precautions should be taken, of course.
Mirror gazing -- A regular hand or wall mirror can be used. It helps if the mirror is round or oval in keeping with the lunar motif.
Tea leaves: Use black tea leaves (peppermint works reasonably well if you're decaffeinated) in a white tea cup.
Embers: Use embers (a wood fire outdoors or in a fireplace) at night.
One note of caution:
Surfaces which provide a random, high contrast visual texture, such as black tea leaves in a white cup or orange sparks in a black ember, are particularly good for the first stage of the scrying process.
However, the vividness of the visual images formed in this way may pull your attention back from the purely mental images, disrupting the natural flow of ideas. Smooth, neutral surfaces, like the surface of a dish of water, a crystal ball, or a black mirror, provide relatively few visual cues to get you started, but if you can make the transition to mental imagery quickly, the visual surface fades into the background.
~from Maat's Book of Shadows