Articles tend to reach far more readers than books. That makes it important to write articles for magazines, especially ones that include author bios or links and mention the title of a book. The articles promote the books.
I enjoy writing articles. I also help authors in CAN write for MTL (More to Life) magazine that's published by the Munce Group (CAN partners with that group to reach out to independent Christian book stores).
My latest book is Stories of Faith and Courage from the Home Front: From the French Indian War through the Wars in Iraq and Afghanistan and I wrote articles for several magazines. I met with editors from magazines at writer's conferences and thought of topics that fit the needs of the magazines and connected to topics in the books.
It helps to check out magazines to find out about the readers, themes, and needs. It helps to keep a list of topics in a book that can be used in articles. It's also good to keep a list of benefits for readers as that brings up ideas for articles that connect to the book. The home front book is great for military families, people interested in history also regions where battles took place in wars that took place in the US. There are stories about teens so I've also written for a teen magazine and offered a link to a file for home schoolers to use. Since stories in it also link to historical dates and holidays those dates provide opportunities for articles. Any type of correlation of ideas opens opportunities to write articles.
Another one of my books is on time management so I write a column for Enrichment magazine abut time. Columns work out well with books on topics that people want to read about regularly.
Magazines are usually planning a few months out (sometimes several months out). That mans ideas for articles should be sumbitted before the book is released.
Another place to submit articles are local newspapers and regional magazines. Authors can submit to their local papers and regions or to regions that are named in the book.
Excerpts from books can also help promote a book. CHeck with the publisher before giving permission for excerpts. Excerpts can peak the interest of readers to buy and read the entire book.