Example (click to enlarge):
In the example above there are two key distinguishing factors between the real label and the fake label. The first is the stitching around the edges. The stitching should be straight and parallel to the edges of the fabric. As you can see in the fake, the stitching is further from the edge than it is in the authentic label. The second thing to note is the size of the text in relation to the label. In this example the fake text is larger.
Example (click to enlarge):
This one is pretty obvious. Not only is the stitching crooked, but the label is cut crooked, the letters are too large, they are located up a little too high, and the label is the wrong proportions (too short). Furthermore, if you look closely you can see that on the fabric content tag of the fake jeans it reads: "Made in Hong Kong." Well, I don't think I have to tell you that authentic Dsquared jeans are not made in Hong Kong.
These fake labels range in quality so keep an eye out.