This post is another result of one of Michael Knost classes. I do highly suggest his online classes to anyone who wants to take writing seriously. Check out his blog to find out more. Anyways, this most recent class I took was all about flashbacks (and backstory, but that's a different post). I found a few "light bulb" moments in the class that just had to share, but this post really is only the tip of the iceberg of what I learned.
The most important thing to remember... Flashbacks should not be used unless there is absolutely no other way the story can be told. Flashbacks carry a built-in disadvantage to even the best of written stories, because it stops the story. A flashback is about something that has already happened. It's over and done with so the flashback lacks immediacy.