The biggest mistake authors make is waiting until their books are published, before thinking about reaching out to media. Books are a golden time/news hook for media, so make sure you nail the opportunity by planning well in advance. Especially in the case of mainstream media, editors and producers feature books exactly when those books come out - ie, if your book is scheduled for publication on November 15, national magazine editors want the book review to appear in the November issue of the magazine. If you miss that window, you miss the opportunity for the book review.
Mainstream national magazines plan about 4-5 months ahead of time. (Right now, they are closing their summer issues and planning their fall ones.) In addition, even in the perfect scenario - when an editor loves your book and wants to move forward with it - you'll need to add on a month cushion for your pitch, to give time for the editor to take your pitch to the editorial meeting and get the approval of the higher-ups. Add to this timing the fact that editors are chronically swamped, and you are likely to need another month just to get the attention of editors. So start pitching long-lead media 6-8 months ahead of time.
National television talk shows and local magazines typically require a 3-4 month lead time, and short lead media - including newspapers and radio shows on the national and local levels, as well as television talk shows on the local level - require a 4-6 week lead time.
If you've just realized that you missed the window of opportunity for a book review, take heart: There are a number of ways to resuscitate a book, even after publication - namely, through organizing a book tour and creating made-for-media events. My next blog post in this series will address how to organize and optimize a book tour - booking speaking engagements at prestigious venues and establishing relationships with VIPs in your field, while successfully generating media coverage.