To make a version of the label that will look authentic when placed over an image of an unlabeled jar of chutney, I started out by rounding the corners:
Next, I added two strips of shade (by reducing lightness on these ares). When performing this task, I viewed the label in context over the jar so that the shade would correspond to the exact points that the jar shape changes:
You can see from the above screenshot that I also added a distortion to the image (image>transform>distort) to create a rounding of the label to give the impression of it being wrapped around the jar.
With the label now placed over the image of the jar, I reduced the opacity of the label to reduce some of the stark contrast. This also allowed the line light reflection on the right hand side to show through the label which helps to define its shape, I used the brush tool to create a parallel line on the left hand side to enhance this effect:
I now have a jar with a blank label template to start adding different label texts to.