Automatic writing is one of the most difficult scrying techniques. It falls into the area of motor automatism.
Basically the mind delivers information by taking control of nerves and muscles of the arm and hand. Professional automatic writers are called autonographists.
In order to automatic write you must achieve an abstracted , receptive state of awareness. Do not focus on your hand or what is being written.
The famous medium Stainton Moses used to receive automatic writing with his left hand while writing with his right hand at the same time. Some people may write without even realizing anything has happened.
Some people have also reported feelings of like electric shocks running down throughthe arm. Others report feeling someone touch or hold their arm and hand and guide the writing.
At first the movement of the pencil may be just circles or lines. A tingling in your arm is a good sign.
Automatic writing is often hard to read and the words are often joined together. Sometimes the words are so small you will need a magnifying glass.
Sometimes words are written in reverse or upside down. Another form of automatic writing is when the practitioner hears words in the conscious mind and then writes them down.
This is how Aleister Crowley received his work "The Book of the Law".