For the sake of simplicity, I'll use the term "subconscious" mind to refer to that function of the mind, which takes care of all the processes that are occurring out of conscious awareness.
Other terms used in hypnosis to refer to this function are the "unconscious", and sometimes "other-than-conscious".Most hypnotists and hypnotherapist's skip the term "superconscious", either out of choice or because they are not quite familiar with it. On the other hand, some hypnotists and hypnotherapists use the term "subconscious" when referring both to the functions of the "subconscious" and"superconscious", at least to some extent.
In strictest terms, "subconscious mind" is that function of the mind that stores individual's past experiences, learnings, memories, emotions, and beliefs. In spiritual jargon the term used to refer to the subconscious is "soul".And you may be familiar with the saying "As a man thinks in his heart", which also refers to "soul" or the "subconscious", because the subconscious is the place where the emotions are stored. This should also give you a clue that one way to access the subconscious mind is through emotions.
The "superconscious mind" refers to the universal storehouse of knowledge from which the individual can draw as much information as his "subconscious mind" allows to filter through. The filters, the guardians at the gate of the subconscious, are the individually held beliefs (in the subconscious mind).
As I have mentioned earlier, the ideas become impressed upon the subconscious mind through your emotions. The more intense are the emotions associated with the idea, the deeper this idea becomes imprinted upon the subconscious. In the extreme situations, this leads to so called "one trial learnings", usually under the influence of shock - one significant experience which becomes deeply impressed upon the subconscious. An example of one trial learning is a person who gets bitten by a snake where this experience becomes deeply embedded.
Another way to impress ideas upon the subconscious mind is through repetition. That's the way we develop habits. Through repetition the behavior becomes habitual and unconscious.
The more intense emotions accompany your ideas, the less repetitions it takes to impress the ideas in your subconscious mind. If you're working with affirmations, they will not yield much results unless they are accompanied by emotions and they match the beliefs that are already in your subconscious.
Generally to change "beliefs" what is required is more information. Yet, even for this new information to become permanent, you need to have a new experience that validates this information.
When you have two conflicting beliefs, the one that will win is the one that is more deeply impressed upon your subconscious. When you're attempting to uproot the beliefs that don't serve you any longer, sometimes it's helpful to bring them out in the open (into your conscious awareness), to examine them and to invalidate them, before you work on installing new beliefs that are more useful to you.
Subconscious mind communicates through symbolic language. Symbolic images, music, metaphors - all work very well with the subconscious. You'll find a lot of symbolic imagery communicated from your subconscious in the dreams you dream while you sleep. Dreaming is very important as it provides an outlet for the release of inner tensions, and for processing of information you imprinted upon the subconscious during the day. You can learn a lot from your dreams, not by consulting some "dream dictionary", but by bringing the contents of your dreams into your conscious awareness and if you don't get the message you can have an imaginary dialogue with the characters in your dreams and simply by asking your mind to clarify the content for you. You're bound to emerge from this contemplation with some insights.
When impressing the ideas upon the subconscious, you may find it even easier if you listen to music - music that either helps you to remain in a relaxed state or music that helps you to elicit the desired feeling.
Your subconscious mind loves rhythm. One way to use rhythm is by listening to music - for example, listening to drumming is one of the proven ways to alter your brain waves and lead you into a trance state. You may also dance and experience the sensations you desire to imprint upon your subconscious throughout your body. One form of dancing you may consider is trance dancing, however depending on your purpose, any kind of dancing will do - as long as while you are dancing your mind is focused upon the idea you desire to impress upon your subconscious mind.
Metaphors can be verbal, as in story-telling. They work better when you are using them to impress the subconscious mind of another person, where the person's subconscious is to get the appropriate meaning. The purpose of these metaphors is to by-pass the conscious awareness, and if you are the one who consciously created the metaphor, there's not much chance that the metaphor would by-pass your subconscious. On the other hand, reading stories rich in symbolism (e.g. fables and fairy-tales) may result in a flash of insight.
Metaphors can be visual, as in alchemical emblems. Aside from the fact that they look very beautiful, studying them and contemplating them, sometimes for a very long time, leaves impressions upon the subconscious mind and results in flashes of insight, deeper insight than may be expressed through words.
You can also draw or create "treasure maps" by pasting pictures of the actual or symbolic images of ideas you desire to impress upon your subconscious mind and place it somewhere where it will be the last thing you see before you fall asleep.
Metaphors can be tangible. Here a physical item is used to communicate to the subconscious mind a desired idea. A person may put on a robe, signaling to his subconscious mind that it's time to get into a trance state. Or a person may get a "success suit" - signaling to his subconscious mind that he now wants to access the state of being a superstar salesman. Some people use candles to represent the idea the desire to impress upon the subconscious - they light the candle and communicate to their subconscious that by the time the candle has burned down, the idea-will be firmly impressed.
Metaphors can also be expressed through symbolic action, as is usually done in rituals - which may be associated with esoteric practices or may be simply ritual actions. Some examples are taking a small stone, and using it as a metaphor for a particular problem and then tossing it in a river - a symbolic action that symbolizes getting rid of the problem (burden).Or, pouring out your heart's woes on a piece of paper in a form of a letter and then burning it - a symbolic action that is meant to transform the emotional state.
Subconscious mind is global (holistic) in nature. One characteristic of this is timelessness - there is only NOW. To successfully imprint ideas upon the subconscious you must experience them as if they are happening NOW. The only time when you can truly experience the feelings and the sensations in your body is in the present moment .You may have an approximate recollection of how something happened in the past , but if you really follow that feeling to experience it to its full intensity (in your whole body), you'll discover that you have spontaneously regressed and are re-living the past - the experience from the past has become a NOW experience. You may anticipate how will something happen in the future, but in order to fully get into that experience (with your whole body), you'll find yourself progressed in the future moment.
Another characteristic of this global aspect is that your subconscious mind does not differentiate between what you perceive as happening only in your mind (as imagined) and what you perceive as being outside of you (as real) - for your subconscious, it's all the same. For your subconscious the "reality" is determined by your feelings.
Your subconscious mind also does not differentiate between how you perceive yourself and how you perceive others. For example, your judgment which may go along the lines that "you are good " and that "the person out there is bad" is simply that "if you were to do what that other person is doing, you'd consider yourself to be bad".Another aspect of this is that you may feel upset with another person, yet your subconscious registers this upset as if it were "with yourself" and activates the release of appropriate poisonous chemicals into your own bloodstream. Ultimately thinking lovely and beautiful thoughts for others has nothing to do with wanting to act saintly, it has everything to do with "self-love" and taking care of yourself.
On the positive side, if you wanted to impress some quality upon your subconscious mind that you'd like to experience in your own life, contemplating this quality in others to the point of identifying with it, works just as well as if you were contemplating it for yourself. So if you focus on prosperity and abundance in general, contemplating the wealth in the universe you'll open yourself to these blessings.