Catoptromancy is a divination technique utilizing a mirror. A very old technique, the mirror was turned to the moon in order to catch the lunar rays. The sought after answers were then thought to appear in characters of blood on the face of the reflection of the moon. This is a very ancient form of crystal gazing. The fact that mirrors were used for divination partly explains why it is considered bad luck to break one.
Historically another method was used for medical prognostications which involved hanging the mirror by a thread over a pool of water. The mirror was slowly lowered until its base touched the surface of the water. Incense was then burnt and prayers were recited. If the image was healthy looking the prognosis was good, if it was greyed and worn looking it was taken as a harbinger of doom.
Catoptromancy or scrying is often considered the most difficult method of divination for several reasons. Unlike more well known methods of divination such as Tarot or runes , scrying can often be much more symbolic and somewhat more difficult to interpret. Most often the answer to intepretation lies within you.
Most people have psychic abilities whether they have discovered them yet, or not. Scrying may well help you to awaken them. Scrying undoubtedly requires patience above all else. At the beginning visions will be very sporadic and vague. Don't despair! Practice, practice, practice! And it will become easier.