There is a set of Ballroom Dance fundamentals that is critical for a new dancer to know and understand. These fundamentals are common to all of the Ballroom Dances. These fundamentals are the basis for all partnership (Four-Legged) movement.
There is a very basic fact that you need to understand before we start. Women in general, learn dancing by "feeling" and men in general, learn dancing "mechanically". If a man can create the feeling, the lady can usually respond correctly. The man and lady have very different roles in Ballroom Dancing. The man initiates and creates a feeling and the lady feels and responds.
Now let's begin with the "Partnership Offset". The dancers do not face each other nose-to-nose in dance position. The partners are offset to the left of each other (a sort of a distant cheek-to-cheek physical relationship). If you are bumping knees and toes when you move, you have lost the 'Offset". The "Offset" must be maintained at all times.
Now that we have the proper physical relationship, let's connect the two dancers together to create a dance partnership. The "Frame" defines the partner's relative physical position to each other in the partnership. The man's arms are lifted with the elbows positioned slightly below the shoulders and slightly ahead of the body. The left arm is extended to the left and bent up at the elbow. The left hand is positioned so the hand is slightly outside of the elbow to the left and the left index finger is parallel to the floor and level with the ladies eyes. The right arm is bent at the elbow so as to slightly reach around the lady. The right hand (with the fingers closed) is the only thing behind the lady. The ladies right hand hooks over the leader's parallel index finger with the thumb side-by-side with the man's thumb. If the thumb overlaps the man's, the man may not be able to let go of the ladies hand to execute turns, etc. The ladies left arm lies gently on top of the leader's right arm with the thumb positioned in the slight recess between the man's shoulder muscle and bicep muscle. The man's frame does not hold the lady. It merely defines her space in the partnership. Do not hold on to the lady!!!.
The next item is the lead. Please be aware that there is not a single lead. There are many leads depending on what you are trying to do. Most new dancers think that the frame is the lead. The fact is the frame is a communication link to the lead. Many new dancers use the frame as a steering wheel to drive the lady. The frame only moves as a result of the body moving (knowing that there are always exceptions to every rule). After the frame has been established, the lead can be initiated.
Before the partnership can move, both partners need to know which foot to be on. The man stands with the weight equally on both feet. He then moves his weight to the right foot, freeing the left foot. This weight change is communicated through the frame to the lady who feels the weight change and matches it. After this point, if the man simply has his weight on only one foot at a time, the lady will respond accordingly. Men, do not end your movements with your weight on both feet. The lady will be lost if you do.
Now that the lady is on the correct foot, how do we actually move? Most men try to be careful and not step on the lady, so they try to move by stepping with the free foot. The free foot movement can't be felt through the frame by the lady. The man must always move by pushing off from the supporting foot. It kind of feels like you are walking up a slight incline which forces you to push off each supporting foot. Remember that the supporting foot is always the boss. The supporting foot (not the free foot) is the only foot that can be felt through the frame by the lady. Moving through the supporting foot moves the body which has the frame attached. Moving the frame through the body moves the lady's space within the frame. Now she can feel the movement. The goal is to allow the lady to move herself to stay within the frame instead of trying to push her around or hold her with your hands.
It is the responsibility of the lady to keep her shoulders parallel to the man. This relationship refines the man's ability to lead the lady. The lady remains in this parallel position unless the man overpowers her into another position such as going from "Closed Dance Position" to "Promenade Dance Position". The lady also returns to the shoulder parallel position at the conclusion of a turn.
The goal in Ballroom Dancing is to become a single "Two-Headed Four-Legged" entity. To do this, the dancers must understand the "Four-Legged Concepts". There are many "Four-Legged Concepts" and those stated above are some of the fundamental ones. "Four-Legged Concepts" are rarely taught in Ballroom Dance "Group Classes". Many of the concepts include "feeling" which requires "hands-on". It is hard enough to teach "feeling" in "Private Lessons" let alone in a Group Class environment. Understanding these various types "Four-Legged Concepts" is what it means to be a "Trained Dancer".
Source: Sharing the Joy of Dance