All mediums, with rare exceptions, pass through minor phases of mediumship before they attain to their true niche in life. One begins to climb from the bottom of the ladder. Just so, as a rule, mediumship begins to manifest itself in a simple manner, and often the individual will not recognize this as true mediumship, because of its very simplicity. These first manifestations, strengthened by work and study and consecration, improve until the individual is ready and prepared for public work.

In mediumship, as in all human activities, there is danger. There is danger in crossing a street, yet no sane person refuses to do so, but merely exercises the sane precautions which will insure them a safe passage. Just so in mediumship it is necessary to recognize and take precautionary measures to insure safe mediumship. One danger which awaits those who rush head-long and without preparation into mediumship lies in the danger of control or domination by selfish or undeveloped spirits. No soul is automatically freed from its errors of thought or disposition merely by having passed through transition from the earth world to the world of spirit. Many of them still retain base personal thought habits and seek to control earth dwellers so that they may gratify their desires and wishes. Not always are these evil spirits, but those who are unspiritual, still thinking in terms of earth's lower aspects.  The [Bible] in the Scriptures clearly state that we must “try to see if they [the spirits] are of God.” [to see if they are good spirits] And this is rule number one to the novice medium, an absolute essential, for safety and progress. The safety of the medium lies in a knowledge of the laws which govern mediumship, in good conditions and environment, and in the constant refusal of all that does not reflect Truth and Purity.

Rule number two is to select with care those with whom to sit, for the emanation from unwise companions taints and retards the reception of genuine and constructive results. The combined thought forces of sitters can, unless the medium is protected by a developed band of spirit helpers, dominate a medium and cause them to do what in their normal condition they would regard with aversion and scorn. Thus to know those with whom you sit becomes a must when beginning the task of mediumship development. Let those of like mind sit together, harmonizing their forces, joining in unity their purposes, and blending in beautiful auric tones their spiritual aspirations, to receive those sublime teachings for which their minds are ready and seeking.

After one has made a study of the Psychic Laws that govern the universe, and the conditions necessary in sending and receiving thought messages, together with the sources of help and safety available, and through these has built up a strong pure character, a resolute will, and a creative faith in God and the power of Truth and Good, then they are ready for the right kind of mediumship, through which will flow the intelligence, inspiration, wisdom, strength and blessings of the angelic world. These qualities attract a  host of loving spirit helpers, who come not only to guide and defend, but to bring great works to the glory of God, and the uplifting of the race.  

This kind of mediumship is the strength of Spiritualism [Spiritism], the Christ-mediumship of ancient times repeated and reborn in our own times. The medium has a new world opened to them through mediumship. They now find the Kingdom of God, the unseen universe, teeming with life and activity, a realm beyond comprehension, yet a concrete fact. Also too, their service to others will be greatly enlarged, and the greatest joys will be obtained from the lifting of fear and sorrow from the hearts of those who are burdened... and in the joy of conscious alliance and partnership, with the unseen Hosts of God, and working hand in hand, with angels [the superior spirits], each task becomes imbued with love and purpose.

Excerpt from  Expanding Your Psychic Consciousness by Ruth Welch, published in 1950.