Writing Tip: Flashbacks - use them sparingly

I’ve read two books in the last month that managed to capture my interest, get a good pace and story momentum going, and then introduce a number of lengthy flashbacks, which killed all forward movement, stalled momentum and introduced back-story that was not needed. When that happens I want to toss the damned book out the window. 

In my humble opinion, the last thing a writer wants to do is stop the story’s momentum in order to introduce back-story. There are good reasons for doing so, but if you’re going to do it, make sure that it is absolutely critical because 1) back-story is seldom as interesting as the current storyline the reader is caught up in so you risk boring the reader, and 2) once you’ve stopped the storyline action to give back-story, it is very difficult to jumpstart that momentum once you come back to it. 
So the question is, how and when to introduce flashbacks.  

Flashbacks are important. Generally, a writer wants to start a story as late in the action as possible. Sometimes s/he may want to start the story long after an event that is crucial to the storyline. So what do you do? You start the story later, but then have a flashback in order to present the needed event or back-story. But understand that you are taking the reader away from the story in order to give him/her background, and background is BORING, or at least not as interesting as the storyline.

So there are a couple of tricks to using flashbacks that help minimize the damage. First, flashbacks in the first half of a story are much less disruptive than the ones that occur late in the story, because at the beginning it is expected that the writer will present information with which to build the story on. As the story progresses, the pacing usually quickens, the momentum builds, and the reader wants to get to the end of the story to find out what happens. So if you halt the momentum near the end, you risk pissing off the reader. So always try to introduce back-story early. 

Another tip is to keep the flashbacks as short as possible. Remember, you’re taking the reader away from the storyline, and the reader wants to find out what happens in the storyline. The longer you drag it out, the more you risk having a dissatisfied reader. 

So my personal rules of thumb when it comes to flashbacks are:
1) Use them only to introduce information CRITICAL to the story.
2) Avoid using any in the second half of the story.
3) Keep them as short as possible.