Before making a long skirt "straight" first, treat the slices of chiffon with a serger or large stitching "zigzag" (first stitch, then fold again and stitch to get more similarity with the serger). Short skirts, regardless of cut, you can sew the same way.
Long skirt on the bias is handled by a small line "zig-zag". The hem will be slightly wavy.
Full skirt on the edges of the handle first serger, and then piping. Chiffon will gain some weight, will cease to gather and a bully.
Wavy fabric will make handling of small "zigzag", while the seam thread fishing line. With the right sewing line should not be touched with a needle and thread pierced.
Processing of shirts and blouses using overlong seam and double binding.