So, you're flipping through your favorite fashionable magazine, and a runway feature comes up. You flip through the few pages and in conclusion think to yourself,
"Wow, those outfits were so ugly! How can anyone think they're fashionable?!". Well my friend, these looks are supposed to look ridiculous. They are meant to be treated like modern art. Well, if they're meant to be treated like modern art, then how do the experts grab the seasons trends from these outrageous looks? Simple! They pick up on certain elements like color, fabrics, accessories, repeated elements, and the basis/origin of the outrageous look. Here, let me give you an example:

Here is a look from Rodarte's Fall 2009 collection. From first impression, the model looks like a furry pastel crayon wrapped in shiny paper. (Ok, that was a really bad analogy but you would not see someone walk down the street looking like this!). The key of dissecting this look is to take out all the key elements of the look. Here is an example based on this look:
Color: pastels, light pinks and purples and a muddy-ish gray boot.
Materials: leather (gloves and boots), sheer fabric top, a loosely knit skirt and a tightly knitted scarf
Theme: cozy, pastel, edgy (leather), warm
Now that you have dissected these key elements from this look, it's time to pick out "normal" looking clothes that would fit in to an outfit based upon this runway look. Here are some ideas for a fashionable look that would come from this runway look:
For the top, probably a nice light pink long sleeved blouse. This material should be sheer just as it is in the runway look.
For the bottom (This is going to be the hardest part because no one wears skirts like the one the model is modeling!), you should probably just trade the skirt for a light wash pair of jeans.
For the shoes, probably a nice light gray leather knee high or thigh high boot, which is toned down from the model's huge boots!
Now since we did not add the loosely knit skirt, we are going to chose a loosely knit sweater/cardigan in probably gray to avoid looking like a pastel crayon.
Now for the accessories, which would be the scarf and gloves. Pick maybe a gray or purple pastel colored scarf to stand out against the pink top and gray cardigan. As for the gloves, if you can find leather gloves in gray, pastel pink, or pastel gray, that's lovely but odds are you will not be able to find them. So, the gloves can be optional.
There is not only one way to interpret a look and there are many different ways to make a wearable look out of a runway masterpiece. As long as you can see the basics, and you understand how to incorporate the key elements in a fashionable way, you should not have a problem. Also, my look idea might not even be the best possibility because I just came up with it off the top of my head with out any clothes to test out my ideas.
So in conclusion, the possibilities are endless to creating a fashionable look based upon a runway look.