Denomination:
The most important design element is the denomination which indicates the face value of a postage stamp. The cost of mailing postal matter varies depending on the size, shape, and weight of the item needing to be mailed. Therefore, each postage stamp has a denomination to correspond to the current cost of mailing. Almost all stamps have a denomination somewhere in their design.
Most current denominations are written in numeric form, i.e. a number with a currency symbol. This format allows for a better understanding of the postage paid by post offices in foreign countries.
Many early stamps wrote the denomination out in words, but the Universal Postal Union later required that stamps on international mail use Arabic numerals, for the benefit of clerks in foreign countries. A number of recent stamps have substituted a textual description of the rate being charged, such as "1st" for first-class letters, or "presorted ZIP+4" to indicate a particular type of bulk mail. Another form of nonnumerical denomination is that used for rate change stamps, in which the timing and politics of the rate-setting process is such that the stamps must be printed before the rate is known. In such cases, the preprinted stamps simply state "A", "B", etc, with the equivalent rate being announced just before they go on sale.
Semi-postal stamps are usually denominated with two values, with a "+" between, the first indicating the actual rate, and the second the additional amount to be given to a charity. In a very few cases a country has had a dual currency, and the stamps may depict a value in both currencies.
Country of Issue:
Almost all stamps will have the country of issue printed somewhere in their design. The exception to this is stamps issued by Great Britain. Because postage stamps were first issued in England, they do not carry the country name, and instead feature a profile of the reigning monarch somewhere in their design. The country of issue can be written out fully or, as seen on more modern issues, can be abbreviated or shortened to fit the design.
Graphic:
All stamps have some sort of graphic element, whether it be a portrait bust, an emblem, a numeral, or any other pictorial design. The first stamps issued in Great Britain, featured a portrait bust of Queen Victoria, which continued to be printed on following issues until 1900. Other countries followed suit depicting busts of their leaders on stamp issues, including Spain, the United States, and many others.
Most stamp issues today have a pictorial design. Pictorial designs vary greatly and feature a wide range of subjects including, but not limited to, animals, famous men and women, world famous artwork, architectural achievements, well known events in history, and more.
Stamp designs are often chosen by a committee, for instance the U.S. Citizens Stamp Advisory Committee, and commemorate a person, special event, or historically important place. These issues are referred to as Commemoratives and are popular among stamp collectors. From time to time, the public will be asked to chose a stamp design, such was the case with the Elvis stamp and the more recent Star Wars stamp sheet.
Many other countries produce stamps, merely for the purpose of stamp collectors. These stamps are often more colorful and depict imagery that would appeal to the collector. Movie figures, cartoons, famous musicians, and other eye-catching pop culture icons have all been featured on stamps.
Additional Text:
In addition to the denomination and country name there is a certain amount of text that can be found on all stamp issues. This text usually makes reference to important information for the issue, such as, the issue date, the name of the person depicted on the issue, the intended use of the postage stamp, important quotes or country mottos, or the name of the printer. Countries that have more than one language may also feature language characters and a variety of written scripts.
Measurements:
The typical shape and size of a postage stamp is a rectangle, horizontal or vertical, measuring 10-30 mm in one direction. However, many countries have issued stamps in the shape of triangles, rhombuses, octagons, circles, hearts, and even banana shapes. Recently, the United States issued a series of Jamestown stamps with a triangular shape that coincided with the shape of the famous Jamestown fort.
Hidden Marks:
Often overlooked, and often hidden, secret marks can be found in many stamp issues from a variety of countries. Some stamp issues will have small design alterations that help distinguish reissued designs. Others may have secret imagery, text, numbers, etc. worked into the design by the stamp designer, perhaps officially or perhaps not. A famous example of a hidden design is the 1987 U.S. issue honoring Rabbi Bernard Revel. The designer of the Bernard Revel issue, drew a very small, and hard to see, Star of David in the Rabbi's beard.