I am a very visual person so I have to lay it all out and then just keep rearranging till I like it...sometimes even as I'm doing the final stitching together!
In general, you want to more or less either do a gradual progression from light to dark or else alternate the two.
As you can see on this one, I did a bit of both in the individual groups of strips. When I was doing the final layout, I switched triangles around so many times it wasn't funny! My goal was to have a fairly even distribution of the colors and the darks, without having any bits next to each other that were exactly alike.
Sorry I don't have a picture of the whole thing so you can see the placement of all of it together.
strip swap quilt
[ATTACH=CONFIG]97148[/ATTACH]