I love piped seams. It’s the costumer in me. The trouble is that piping can get expensive, but making your own is super-cheap and easy and then you can have silk piping which is, I’m pretty sure, one of the high points of human civilization. If you already know how to make bias tape, you’re half way home!
You will need bias tape (1 – 1 1/4″ wide), some form of pipe-filling, and a few minutes. Now, there’s an official right substance to use inside of bias tape. You can buy it at the fabric store. Sometimes I use it. I am most likely to use plain old cheap acrylic yarn in any kinda pukey color that I can’t imagine knitting with. (I have a lot of spare yarn.) If you want piping that will also be very architectural/help stiffen an edge or hem, try a heavier nylon monofilament. Weed-whacker line works right nice.
Here’s how you do:
Ideally, at least one of the threads in your machine should more-or-less match the color of the bias you are using.
If your bias has joins in it, make sure that these are going on the inside of the piping. If you come across a seam allowance and it is on the outside, go ahead and cut the piping right there. There’s always a reason to need a small bit of piping. There’s never a reason to need piping with the seam on the outside. ;)