I came up with an analogy about plotting that works for me.

Me, I don't like to plot. Like I think I said elsewhere, I like to let my characters tell me the story. I don't like to shoehorn the events that come up as I write into some master plan I wrote weeks or months before. If I don't, I find everything just kinda works out as I go along. Plus my story entertains me as I write it. I get to watch it unfold before my eyes.

This obviously won't work for everyone. Some people prefer to plot everything in advance. That keeps the story tight, but I find it kills my urge to write.

I thought plotting everything in advance was "the" way until I found out Stephen King doesn't plot either. Whew.

Now... I do plan. I create reasonably detailed character sketches, think up a theme and a major conflict, create maps maybe.

And I do I plot a little, but only as I go. I always keep in mind my next set piece, or mini-climax, that the scenes I'm writing are leading up to.

So I think of it like hiking up a mountain. I can see the next peak, and I can see the summit, but I can't see all the peaks along the way. But that's okay. I know I will reach the summit eventually if I just keep my eye on the next peak.

Then once I reach the top, I take a breather, then go back down and start editing my trail. I go up and down a few more times. Each time, I groom the trail by removing all the stones and sawing away the fallen logs and big roots. I make the going smoother for the next guy, who will hopefully be my reader. It should look like a paved road by the time I'm done, and he will never know I didn't plan it all out in detail in the first place.

To extend the analogy...

It's okay to see a peak, head toward it, then suddenly see another trail and take it instead. You changed peaks, but you still have the same final destination. This makes for a more interesting journey, and your reader will probably be thrilled.

However, it is not okay to see a different mountain and go over to it instead. That means you have to climb back down the mountain and start all over on a new mountain. Your reader is going to be awfully pissed at you for dragging him along for nothing. You should just start him on the more interesting mountain in the first place, and save the first mountain trail for another story.

So when a protagonist dies halfway through the story, it's like changing mountains. I hate hate hate that.

Or what Melville did at the beginning of Moby Dick -- he switched protagonists altogether. That would never be tolerated by today's editors.