My go-to reference for this technique is Lynda Maynard's book, The Dressmaker's Handbook of Couture Sewing Techniques. Sew Maris also gives a nice review of this technique in her Craftsy blog post.
As in many things related to sewing, testing is so important. The type of fabric; weight of interfacing; adding additional fabric to give a quilted effect; thread color and weight; and stitch length are all considerations that need to be tested before moving on to fashion fabric.
For my Sailor Collar Moto Jacket, I used channel stitching to accent the peplum, cuffs and collar. The peplum is stitched using my regular cotton thread, while the stitching on the collar (faux leather) is done with a heavy topstitching thread.
The jacket is a stretch denim fabric and the collar/cuffs are faux leather. All of the facings are stretch denim interfaced with a lightweight fusible. I could have added a layer of flannel on the inside to add further dimension for a more "quilted" look, but I opted for a flat effect.
What is cool about channel stitching is that it can create a new texture -- the peplum piece has much more structure and a defined shape due to the rows of stitching. The down side of this is that, depending on the amount of stitching you add, you need to take shrinkage into account, as all those rows of stitching will "shrink" the piece. Again, testing is key!
Stitching around corners is tricky, and I have to admit the above isn't perfect. However, it helps to decrease the stitch length around the corners and, while I didn't do this, it might help to chalk-mark the corner distances so each row is even. I was lazy, so I just eye-balled the distances and hoped for the best!
Here's a project I'm currently working on that uses channel stitching on the collar and front flap piece. The fabric is a silk/wool blend that is interfaced with a lightweight fusible and the facing is a china silk lining fabric.
In this case, the stitching practically melts into the fabric -- it is very subtle and, because I limited the rows of stitching, it doesn't really add much structure or shape. This is a wearable muslin, so I think for the final garment, I'll choose a thicker topstitching thread in a slightly more contrasting color to make the stitching stand out a bit more.
Some thoughts on channel stitching:
1. Test the fabric, interfacing and thread combination you plan to use to make sure the effect is what you originally envisioned. This is also a good time to test the stitch length you like; the spacing between rows (I like 1/4 inch); and whether you need to worry about shrinkage.
2. Take shrinkage into account. If you have a lot of rows of stitching, the piece will shrink slightly, depending on the fabric, thread and stitch length you are using.
3. A walking foot helps to keep the layers of fabric from shifting too much, especially if you choose to add a layer of flannel or other fabric for a more "quilted" effect.
4. Some people mark their rows of stitching with chalk or other marking method. I just measure off 1/4 inch from the edge for the first row and use my stitch guide/machine foot to maintain an even distance between rows. It is difficult to keep the rows evenly spaced and straight, so I end up sewing each row very slowly.
5. I start and stop each row of stitching by decreasing the stitch length -- I do not backstitch, as I think the smaller stitches give a cleaner finish.
While this technique is time-consuming to do, it is a beautiful design detail. I hope you have the chance to try it!