All stamps can be divided into two categories: canceled and uncanceled. Canceled stamps are those that have actually been used to send a piece of mail. Uncanceled stamps, though not necessarily new, have never been so used. A canceled stamp, when in use, is attached to a cover either an envelope, postcard, or package. The process of canceling further binds a stamp to its cover. Therefore canceled stamps should probably not be removed from their covers. This is especially true of stamps from before 1900, stamps canceled in any unusual way, and stamps that were canceled on the first day of issue.

Any cover that shows it was sent by or to a famous person should be kept intact. Unusual cancellations are those made on ships or trains, those made in a color different from the usual practice, and those in which the canceling machine had an unusual design.
 
Sources.

There are several sources for stamps. The most obvious is one's own mail. Unfortunately, stamps received this way are not likely to have much value, unless they come from unusual foreign places. Some small nations have made a minor industry of printing stamps for collectors worldwide. Liechtenstein, in Western Europe, is the most prominent such country. San Marino, in but not part of Italy, also promotes the sale of its stamps, as does Vatican City in Rome.

New stamps can be purchased from post offices. Since 1921 the United States Postal Service has maintained a Philatelic Agency in Washington, D.C., for selling stamps to collectors only. Larger post offices in major cities have counters that specialize in selling new issues and other stamps to collectors. Stamps are sold in sheets, blocks of four, and occasionally in small souvenir sheets.

It has become common to sell commemorative stamps honoring historic events or well-known people. In the United States the likenesses of living persons are not used on stamps, but other nations frequently use such portraits. British stamps, for instance, carry a likeness of Queen Elizabeth II. One of the first commemorative stamps was issued in 1888 by New South Wales in Australia on the 100th anniversary of the colony's founding.

Both canceled and uncanceled stamps can be purchased from stores that specialize in coins and stamps. Some hobby shops also carry them. One must, of course, pay market value. As with any hobby, there are magazines for stamp collectors, and these carry advertisements of stamps for sale. The stamps are usually sold in packets, sets, or approval sheets. Packets are envelopes containing a specified number of stamps. A set is composed of stamps bearing the same design but having different values imprinted on them. (Some sets have stamps of varying design, all on the same subject.) Approval sheets are sheets with stamps on them that dealers send out on request. The buyer picks out those he wants and returns the rest, along with payment for those that are kept.
 
Catalogs and journals.

During the first 20 years that postage stamps were in use, the widespread popularity of collecting them prompted the publication of stamp catalogs. The first lists of collectible stamps were published in France in 1861 by Oscar Berger-Levrault of Strasbourg and by Alfred Potiquet of Paris. The eagerness with which collectors bought the lists led Berger-Levrault to issue a new edition later in the same year. In 1862 catalogs were published by J.B. Moens of Belgium and by Frederick Booty, J.E. Gray, and Mount Brown in England.

In 1863 E. Stanley Gibbons published the first edition of a catalog that has remained standard reference in Great Britain. The two leading lists in the United States are the ‘Scott Standard Postage Stamp Catalogue', founded in 1863, and the ‘Minkus Stamp Catalog', started in 1954.

There are many informative magazines and journals on stamps and stamp collecting. Some of these are published by collectors' clubs. The magazine with the largest international circulation and some of the most comprehensive coverage is Linn's Stamp News, founded in 1928. Other journals for collectors include The American Philatelist (1887), Canadian Philatelist (1950), The Collectors Club Philatelist (1922), Gibbons Stamp Monthly (1927), The London Philatelist (1892), and Mekeel's Stamp News (1891).
 
Albums.

In 1862, a year after the first lists were published, albums for stamp collectors appeared on the market. Both the French and English editions were issued by Justin Lallier in Paris. Albums have proved the easiest way for collectors to assemble and arrange their stamps. For beginning collectors, the simplest approach is to buy one that has sections for different countries, with squares printed to indicate where each stamp should be placed and with illustrations of each type of stamp. Experienced collectors who specialize in specific types of stamps will probably use a blank album. Albums can be bound volumes or loose leaf.

Careful collectors do not handle stamps with their fingers. To avoid damaging them with moisture or grime, the collector uses a set of tweezers called tongs. Stamps should not be pasted in an album. Instead, they are affixed with peelable hinges, narrow strips of transparent paper gummed on one side.
 
Organizations.

Clubs and societies for stamp collectors can be found around the world. The Philatelic Society of London (now the Royal Philatelic Society) was founded in 1869 and the American Philatelic Society in 1886. There are a great many specialized societies: the American Air Mail Society (1923), the American First Day Cover Society (1955), the Armed Forces Stamp Exchange Club (1954), the British North America Philatelic Society (1943), the British Postmark Society (1958), the Canadian Air Mail Collectors Club (1969), the Chemistry and Physics Study Unit (1979), the China Stamp Society (1936), the Collectors Club (1896), the International Federation of Philately (1926), the International Stamp Collectors Society (1970), the Maritime Postmark Society (1939), the Space Topics Study Group (1957), and the War Cover Club (1937).

Many organizations hold annual or other scheduled meetings. The first international gathering was the Congress Internationale des Timbrophiles (International Congress of Stamp Collectors) in 1878. Among the larger societies are the Philatelic Congress of Great Britain (1909) and the American Philatelic Congress (1935).

In addition to the clubs, there are some outstanding stamp libraries. One of the best in the United States is the library of the Collectors Club of New York. Others include the Philatelic Library of Los Angeles, the Klein-Deats Philatelic Literature Collection in the Philadelphia Free Library, and the library of the Philatelic Research Society in Oakland, Calif. In London the Royal Philatelic Society has a library. The postal museums of Europe contain some excellent collections. Among the most notable are those in Berlin, The Hague, and Stockholm.

In the United States there is a large collection at the Smithsonian Institution in Washington, D.C. The British Museum probably has the finest stamp collection in the world.

New Stamps.

The United States Postal Service in 1990 introduced a new kind of postage stamp a no-lick plastic stamp whose design specifications allowed it to be sold through automatic-teller machines. The pressure-sensitive polyester stamps, sold in peel-off “sheetlets,” were extremely durable and stuck to envelopes better than gummed-paper stamps. Canada also offered peel-off stamps at a higher price. Some countries with high humidity, for example, Sierra Leone and Tonga, had had such stamps for some time.