In Media Res: I agree with you that it's good to start before the serious stuff gets rolling, but starting mid-action doesn't necessarily mean starting in the middle of the important action. As a variation on Sam's example, consider this:
The cereal was soggy already. How long had John been sitting here, staring at the empty seat across from him? Four months, two weeks and six days. His glance slid to the brick fireplace, and the faded wedding photo on the mantle.
Those are my top-of-the-skull tidbits. Great topic!

I like the comments so far and am looking forward to reading more.

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