The example here is a great jacket, but the sleeves were too full. Slenderizing them gives the jacket a whole new look!
This is basic sewing stuff, and I am a basic sewer. You can do it yourself, it's easy!
You will need:
Scissors (fabric scissors are best)
Sewing Machine (you CAN do it all by hand, but it will obviously take longer)
Fabric Crayon, or other marking tool
Step 1: Determine the Correct Fit
Put on your jacket and pinch one of the sleeves at the seam (starting from your armpit to your wrist). You will use pins to mark where you will be sewing. Be sure to not pinch around the arms too tight, or you will have trouble bending your elbow. The most critical part seems to be on the forearm a few inches down from your elbow... determine the maximum amount of fabric you will be taking in at this point.
You should do this with only one sleeve for now. You can do the other one later.
Step 2: Detach the Sleeve Lining
If your sleeve doesn't have a lining, skip this step.
If it does, cut the threads that bind the lining to the jacket sleeve. In this example, this step was easy; the lining was easily detached from the top hem.
Peel back the lining to expose the jacket's original seam.
Step 3: Mark Your Seam
Where the original seam meets the armpit, taper your marking towards this seam in order to blend the new one with the old.
Step 4: Sew!
Sew from the end of the wrist to the armpit along your marked line.
Step 5: Test, Copy, Sew Again
If not, you'll need to rip out the stitch and adjust your measurements .
Transfer your correct measurements to the other sleeve and sew it also (after, of course, you open up the sleeve lining if it is present).
Step 6: Finish
Now you can finish by re-attaching the jacket to the lining. If you tightened up the circumference of the sleeve a lot, you may not be able to fit it on your sewing machine, like in my case. So I had to hand-sew.
Enjoy the new look!