Captions Sell the Article: The typical magazine reader flip through an issue to see what captures the eye. If a photo or illustration captures attention, the viewer is then likely to read the caption. If the caption conveys useful or intriguing information, the reader may decide to read the rest of article.
Captions Summarize Article: Use illustrations and captions to summarize the article. That way, the reader gets useful information -- and you get your point across -- even if the reader does not read the body of the article.
Tell a Story with Captions: A caption should do more than just identify the content of an image. It has the opportunity to tell a story. Even a short caption can explain who, what, when, where, how, and why.
Caption Stands Alone: To the extent practical, a caption should be able to stand alone so the meaning of the photo is understood even before someone reads the article. This means, for example, that abbreviations and jargon should avoided in the caption, or at least succinctly explained.
Search Engines Like Captions: When writing for the internet, captions help search engines find your illustrations.
Editors like Captions: Editors hold the key to getting your message out. So anything you can do to make the editor's job easier will help you get exposure. I found this to be the case when Carolyn Schierhorn, the former editor of Masonry Construction, expressed her appreciation for an article I contributed: “It was a pleasure to receive an article so well-organized and mechanically flawless that almost no editing was required. That you included detailed, beautifully written captions as well is nothing short of miraculous.”
Finally, remember to include copyright notices and other identifying information required for use of the photo or artwork.