In part two of my three-part series, I will talk about the importance of texture in addition to shape and how to recognize appropriate textures.
Texture Recognition
For the most part, the discussion of texture relates to making the fabrics in an outfit harmonize with each other in order to achieve a beautiful effect (though I have come across a discussion linking fabric texture and modesty, I don't think you can make an argument that certain textures are inherently immodest). Usually, you don't have to worry about texture if you choose a dress or suit with only one type of fabric, as shown above. There are exceptions, however . . .

Granted, this dress has shape problems as well, but the point is that some textures are just not going to look fitting for an entire outfit. Another example is that feathers, except as a costume, do not achieve a serious effect:

Now, one might think that recognition of the texture of clothes relates to the sense of touch. Actually, the feel of the fabric is largely irrelevant. What matters, as always, is how it LOOKS. Congruity is the main point. That doesn't mean you can't experiment with textures, though. Sometimes a bit of texture will make a gown exquisite:

Generally, we know that silks, satins, sequins, and chiffons go together: we see them ubiquitously on formal wear. What about more everyday choices? Again, the textures must harmonize. Here's an example of a slightly incongruous fabric pairing:

Yes, the colors and shape aren't the greatest either, but what makes it look especially odd is the heavy textured dress against the silk printed blouse. Are there hard and fast rules in this area? Probably not. Nevertheless, you can develop a sense of it from the bad cases. I just can't resist giving you another texture nightmare:

Resist dressing in rafia and popsicle sticks! Other than that, don't be afraid to be creative. Maybe a couple general rules could be not to pair two "loud" or heavy/prominent fabrics with each other and not to pair a more formal with a more casual fabric--like cotton jersey with chiffon, for instance. In these cases, I'm talking about the two main fabrics used for an ensemble; oftentimes, an accessory or accent in an oddball or not strictly matching fabric (maybe even feathers, who knows!) may work. For ideas, you can look at reliable catalogs or online shopping sites. This one and the one at the top of the post come from j jill:
As you can tell, the suggestion of texture does a lot for overall effect. Whether soft, smooth, shiny, nubbly, lacy--one can't ignore the textural quality of the fabrics of dress. Here is a final example that brings together shape and texture with very appealing results: