Mediums
The spirit world is of a higher vibration than the earth plane. You can raise your vibration high enough to make contact with the spirit world and the people in it. Conversely, people in the spirit world can lower their vibration and touch down into the earth plane.
Mediums are people who are able to raise their vibration high enough to contact and communicate with your loved ones, guides, and teachers in the spirit world. A medium becomes the message bearer for the guides, teachers, loved ones, and other spirits around you who want to talk to you, let you know that they love you, and help you progress spiritually.
Personal responsibility and Spiritual Progression
Spiritualism teaches that you are responsible for your own happiness and unhappiness. Your happiness and unhappiness are largely determined by how you look at things. Negative things do happen and you have no control over some of them. But you can control your reaction and the point of view you take in dealing with the negative. Besides, an uncontrollable negative in your life today can have a positive affect on other areas of your life years later.
You can make changes to improve yourself and your life, which in turn affect your vibration. Spiritual progression takes time - it doesn't happen in a minute or overnight. You have to make a start in the right direction first. Your guides and teachers will help if you sincerely ask.
Natural Law
How do you progress spiritually? There is a set of rules to live by called Natural Law. In practice, they are like the laws of physics - unbreakable. It is like dropping a glass from your hand - it always falls to the ground. There are no exceptions to Natural Law. The more you live by Natural Law and apply it in a positive way, the higher your vibration. The closer you come to God.
Law of Vibration
You are already familiar with the Law of Vibration - all things vibrate and positive thoughts, positive actions create a positive (higher) vibration.
Law of Attraction
The Law of Attraction states that like attracts like. The simplest way to see this law in action is to look at your self and the people around you. The people you are the most comfortable with and relate to are of a "like mind" in some way. Look for the similarities in the people around you - family, co-workers, and friends - their attitudes, opinions, outlook on life and spiritual makeup. Now think about the people who you can't stand, are very uncomfortable with and don't want to be around unless you have to. See the difference? Like attracts like.
Apply this law with the Law of Vibration. Your vibration is determined by who you are and how you live your life. People with a similar vibration will be attracted to each other (on a spiritual level). If you are a hateful, jealous and cruel person then you will attract people who are hateful, jealous and cruel. If you are a kind, loving, and warm person, then you will attract people who are kind, loving, and warm. The Law of Attraction operates in the spirit world also. You tend to attract the spirit people that are "just like you". As you live your life closer to God (and Natural Law) your vibration raises and people of a higher vibration will be attracted to you both on the earth plane and from the spirit world.