How to Copyright your Photos
By Peter Marshall
(Source: http://photography.about.com/cs/businessmatters/ht/ht_Copyright.htm)

• You do not have to do anything to established copyright in a photograph—all photos (except possibly some copy work) are automatically copyright.
• Optionally you can register copyright with some national bodies. Doing some may make it easier to claim breach of copyright and increase the amount you can claim in that country.
• For the USA, go to the Library of Congress web site and download the forms listed there—they are in Adobe Acrobat format.
• The fee of $30 [USA] can cover any suitable collection of photographs. Read all the instructions and follow them or your form will be returned! (I have personally experience this! —TPNet)
• You can also add a digital "water mark" or image which creates a marker in the picture identifying it as yours, but this may not be very effective. (In our photo galleries you will notice our copyright image (right) in a corner of the image. —TPNet)
• Whenever you publish a photograph, particularly on the World Wide Web, it is a good idea to use a copyright statement, such as "©2005 TrainPixs Network" on or near the work as a reminder.
• Copyright generally last for 50 years after the death of the photographer.