Lining in jackets makes the garments more comfortable to wear and easier to slip off and on. Linings also protect the seams, helping the jackets last longer. However, when it comes time to alter the jacket, linings make the task more difficult. This is because sewing through the lining and outer fabrics at the same time leaves a rough finish. Separate the lining from the jacket in order to have the best result.
Locate the hem's seam and pull the fabric on either side of it taut to expose the stitches. Use the seam ripper to remove the stitches. Using the hem as a starting point is best because it creates a wide entry point for the tailor, whether the seams need to be taken in or the sleeves shortened.
Mark the area to be altered with pins. Keep to the original seam and hem lines to ensure that the jacket retains its original finish. Pin the fabric in to fit your body until the jacket takes on the style you desire. Ensure that all your pinned seams are symmetrical.
Baste the seams in place and try the jacket on once more. Basting stitches are done with the widest possible stitch on your sewing machine, since they are easy to remove if the seam is incorrect. If it requires no further alterations, sew over the new seams with a narrower stitch to hold the seams in place.
Cut away the excess fabric and finish the seams so they do not unravel. Repeat the process with the lining so that the seams meet on the inside of the jacket.
Turn the jacket right side out and press the hem back into place using the iron. Whipstitch the lining back to the jacket by hand to make sure that the lining remains invisible from the outside. The whipstitch is done by sewing a series of small diagonal stitches to connect a small bit of fabric from the lining and hem.