In most heraldic jurisdictions, the Dexter side is the male side and the Sinister the female. Most people have been right handed and the principal weapon for hand combat, the sword, was carried in the right hand and subsequently, the right side of a person (Dexter) was held to be the most important. You've probably heard the expression about someone being someone else’s 'right hand man' - this stems from this practice as well. There are a set of parameters within heraldry that dictate that all things do something in a particular way and that is what is called the 'norm' or 'default'. Anything different from the 'norm' has to be spelt out in the official blazon. As a norm, all things with some sort of identifiable attitude face the Dexter. If they differ from this, it has to be clearly indicated in the blazon (heraldic description of the arms).

The male (Dexter) side has always been the dominant side and when blazoning arms, the male side is dealt with first. This has nothing to do with being sexist (or has it??), but in times past the woman brought things, including herself, to be part of her new husband's estate (very rarely the other way round) as the family name is taken from the male side of the family. A woman coming into a marriage, by custom (the norm again) took her husband's surname. The Dexter side of the shield was the male lineage and followed the male bloodline and surname and always takes that position.

The same sort of thing can also apply with quartered shields (made up of three or more sets of arms) - there is a definite pecking order with the top left (Dexter chief) being the predominant position (1st quarter) followed by the bottom right (Sinister base) as the 4th quarter, then the top right (2nd quarter) which is the Sinister Chief position, and finally the bottom left (Dexter Base) which is the 3rd quarter.

The fact is that a single armorial achievement (coat of arms) of a quartered shield, made by dividing the field by a vertical and horizontal line, or a cross, is just another method of partitioning the shield, just as a shield can be partitioned into four by two opposing diagonal lines. The splitting of a shield by partition lines is one of the many ways to make up different shield designs as the lines themselves can be different - i.e.: zigzag, castellated and several others. These lines of partition have no specific meanings other than those in the mind of the herald who designs the arms.

Some of the above may appear to be complicated, but the more you become acquainted with heraldry the easier it becomes.