You can use pre-made, packaged piping or make your own. I'm using regular old packaged piping here.
Here are some pictures of this technique used on a kimono sleeve. First, you pin the piping to the seam you want to finish. The corded part of the piping should sit just to the garment side of the seamline. In the picture below, there's a 5/8" seam allowance, and the piping cord is just above that 5/8" mark. Measure your seam allowance as you pin the piping in place.
Next, stitch the piping in place with a zipper foot, getting as close as possible to the cord.
To topstitch, use a zipper foot to stitch close to the piping cord on the outside of the garment.
Voila! An easy finish that's both clean and decorative.