The Language of Heraldry

Now, while the shield itself is often called a Coat of Arms, there are many other terms dealing with the coat. (Incidentally, it's called a "Coat of Arms" because originally the warriors (not always Knights) wore a surcoat over their armour, on which was painted their personal symbol. But, in common blazon, the term now refers to the set of symbols and patterns awarded to a single individual as their personal symbol.) There are other parts to some awards besides just the shield itself. A full Achievement of Arms consists of a Helmet, a Crest, Mantling, Supporters, and a Motto. I will be dealing mostly with just the shield, but you can check out Armorials for a discussion of the full achievement.
Usually a coat of arms is found on a shield shape, but in addition to there being several different styles of shields, there are also many other shapes that a coat of arms might be found upon (lozenges, banners, and circles are not unheard of).

Two fundamental terms in Heraldry are Dexter and Sinister. They refer to the left and right sides of the shield. Trivialists might notice that in Latin, Dexter actually means "right," and Sinister means "left," however, Heralds describe the shield from the shield bearer's point of view - thus, his right, or Dexter, is to our left - and the Dexter side of the shield is to our left. Similarly, Sinister is then to the right. An object specifically placed in the right hand side is said to be in Dexter, but if it is merely pointing towards that side, it would be said to be to Dexter. Sinister follows the same rules.
Three other terms of importance are Chief, Fess and Base, which refer, respectively, to the top, middle, and bottom portions of the shield. Like Sinister and Dexter, something can also be placed in Chief, in Fess or in Base, or be to Chief or to Base in orientation. If not otherwise blazoned, most will be assumed to be centered, or in Fess, thus in Fess is an uncommon term. When blazoning, it is not neccesary to capitalize any of these terms.

The Order of the Blazon

To properly blazon a shield, you must understand the order in which the elements of the shield are expected to appear. Blazons are set up in a logical order so that any two Heralds, no matter where, can understand what is meant by the blazon.

In general, a blazon works from the field, or background, out towards the viewer - with charges on top of other charges appearing later in the blazon - and then from the viewer's left to right and top to bottom. So something appearing in the upper right hand corner would be blazoned after something in the upper left, but before anything in the lower left. It might help you to really think of the shield as a three dimensional painting - with the base coat going on first, then any decorations added later.

This base coat is known as the Field, and any decoration on it is known as a Charge. Charges can range from animals, to weapons, to letters, or even weird shapes. There are certain geometric charges common to all heraldry: these are called Ordinaries. In order for Heralds to keep all of this straight, they have to follow a specific order when blazoning.

The very first thing in a blazon should be the background, or Field. Next comes the most important Charge on the shield, usually an Ordinary, followed by any lesser charges around it. Thirdly will come any charges placed on the primary charge or ordinary. Next appears certain unique charges that do not normally appear in the center of the shield, immediately followed by any charges appearing on those. Lastly are any marks of Cadency, or relationship.

The Field

The field can be a single colour, multiple colours, or even a pattern. The colours used by Heralds are broken up into two categories: Tinctures and Metals. The colours yellow and white are known as Metals, but in Heraldry, white is called Argent (for silver) and yellow is known as Or (for gold). The most basic of the tinctures are Gules (red), Azure (Blue), Vert (Green), Purpure (Purple) and, despite the fact that it's not really a colour, black, which is called Sable. (There is more to it than this, but it's covered more in depth in Tinctures.)
The most commonly quoted rule in Heraldry is the "Rule of Tincture" which states that "Colour should never appear on colour, nor metal on metal," which basically means that something that is coloured with a tincture should not appear on top of something that is also coloured with a tincture, and the same goes for metals. However, colours may freely appear on metals, and vice versa, and the rule does not apply to adjacent divisions of the field, or when dealing with varied patterns of the field. For example, a white lion can appear on a black background (metal on tincture), but a blue lion should not (tincture on tincture). This is a rule frequently ignored in Amtgard heraldry. Historically, this rule was to make sure that there was enough contrast between objects on the shield, so that it could be clearly seen across a field. When blazoning, Tinctures and Metals should always appear capitalized, for clarity.
A field can be of a single colour and have small objects "scattered" on it as a pattern - this is called Semy. For example, a black field with white polka dots would be blazoned "Sable, semy of Roundels Argent." (Roundel is the blazon for a circular spot). Certain patterns of semy have their own unique names, such as the semy-de-lis, which is a scattering of the Fleur-de-Lis shape (a sort of stylized flower). See the page on Semy for more details. There are also special names for some other patterns, such as a group known as Furs. Like Tinctures and Metals, Furs should also be capitalized in blazons, however, in regards to the "Rule of Tincture," Furs are considered "amphibious" - that is, they may appear on either Tinctures or Metals, and either may be placed on Furs. The most common furs are Ermine, Vair and Potent. Again, this is a very simplistic look at this - for more information, see Tinctures.

A Field can be of a single colour or fur, or it can be divided, or Parted, into multiple parts, and each one coloured (or furred) separately. Each of these lines of partition has it's own name. A vertical part is known as party per pale (or just per pale), while horizontal is per fess, and of course, there are many others. Each line can also be decorated in in different ways, such as by being Wavy, or Engrailed (which is a bunch of semicircles, sort of cloudlike). There are many other kinds of divisions and decorations, to learn more, see Lines of Partition. When blazoning lines of partition, it is not neccesary to capitalize them, in fact, to avoid confusing lines of partition with Ordinaries (many of which have very similar names), it is best not to.

Here are some examples of blazoning the field:

Vert.
Plain green (Vert) - nothing more needs to be said.

Per fess engrailed Argent and Azure.
This means that it is divided in half, horizontally (Per fess) and the line of division itself is made of semicircles (engrailed) and the top half is white (Argent) while the bottom is blue (Azure). Following the rule of top-to-bottom and left-to-right, you blazon the top colour before the bottom colour, or the left-hand side before the right-hand side.

Charges - The Ordinaries

Anything placed on the field is called a Charge, and in fact, anything with something else on it is said to be "Charged with" the other object. The most common of these objects are known as the Ordinaries. Ordinaries are geometric charges that (generally) go from one edge of the shield to another. While the width of the Ordinary may vary, based upon whether or not there are any charges on it, or around it, generally, they will take up about one third of the shield's area. Ordinaries, like lines of partition, can be any Tincture, Metal, Fur, or other pattern, have their edges decorated, or even be semy'd. There are ten commonly accepted Ordinaries, such as the Fess (a wide horizontal bar), the Pale (a wide vertical bar), and the Cross (a horizontal bar crossing a vertical bar), as well as many others. Narrower variants of Ordinaries are known as Diminutives and, like Ordinaries, they run from edge to edge. However, Sub-Ordinaries are geometric charges which do not neccesarily touch the edges of the shield at all.
Ordinaries are almost always found in a specific orientation, and at a specific position on a shield. Some Ordinaries, however, can appear upside-down from their usual position. This is termed inverted. The Bend, which normally appears as a bar running from the upper left to the lower right, can be mirrored, to run from the upper right to the lower left - in this case, it is called a Bend Sinister. And, finally, if an Ordinary is higher on the shield than it would normally be, it is said to be enhanced, and if it's lower than normal, it would be abased.
When blazoning Ordinaries, you need to follow a specific order. First, if there is more than one , the number must be stated. Next comes the actual name of the charge, followed by any words describing it's position or decorations, and lastly, the colour; however, an exception to this is if the Ordinary is immediately followed in the blazon by one or more charges of the same colour. In this case, the colour of the Ordinary is not mentioned, but is assumed to be the same as the following charges, where the colour should be mentioned. Although the Ordinary is mentioned first, it is not mandatory to have one, and in fact, although it is uncommon, it is possible to have field with nothing else on it.

Here are some examples of blazoning Ordinaries:

Or, a Fess Vert.
Simply, a yellow (Or) shield, with a wide green horizontal bar in the center (Fess Vert).

Sable, a Pale wavy Argent.
Black (Sable) with a wide white wavy vertical bar in the middle (Pale wavy Argent).

To learn more about the Ordinaries, check out Ordinaries, Subordinaries, and Diminutives.

Other Charges

Other objects appearing on a shield are known simply as Charges, and can range from simple geometric shapes, to strange animals, to common objects, and can appear in all Tinctures, Furs and Metals. Like Ordinaries, most charges have a particular orientation. Some charges are perfectly symmetrical, and thus, have no set orientation. Bilaterally symmetrical charges, however,
When blazoning a charge, you must first mention the number of charges you are describing, followed by the name of the charge, it's facing and orientation, and it's colour. Like Ordinaries, the colour can be left off if the very next charge or charges are the very same colour. If the charge is the same colour as the field, (only possible if it is charged upon an Ordinary or other charge), it is said to be of the field. If it is of another colour previously mentioned in the blazon, then instead of the colour, a place number of the original colour is used, such as of the first, or of the second, etc. You should always blazon each kind of charge separately, so as to minimize possible confusion.
If the placement of the charge or charges would not be obvious by the other things already on the shield, then the placement also needs to be specified. For example a single charge all alone on a shield is assumed to be in the center. If there is a Bend on the shield, however, it would need to be noted whether the charge appeared on the Bend itself, ("...On a Bend (colour), a charge"), in the upper portion, ("...a Bend (colour), in chief a charge..."), or the lower portion ("...a Bend (colour), in base a charge..."). If no placement was noted, it would be assumed to be in the upper portion, or, in the case of a Pale, in the Dexter portion - both positions being considered more "honourable."
Three charges together on a shield are assumed to be placed two in chief and one in base., so if all three were meant to appear in the top, it would need to be noted. Other numbers of charges should be as evenly divided as the shield's divisions allow. If it is not possible to evenly divide the charges, then the greater number would appear in the chief, or dexter sides. In such cases where one charge is surrounded by other charges, it is said to be between the other charges, as in a Fess between three Roundels Or.

Other Terms

Part of what I enjoy about heraldry is the fact that even traditional heralds enjoyed a good pun. In fact, there are many historical examples of Coats-of-Arms that are really just plays on words. For example, the Castiles of France have on their shields a castle - an obvious play on words. Similarly, the Leon family uses the lion (French "Leon" meaning lion.) This practice of using word play to create a coat of arms is called Canting.