Take this shirt for example. Cute detail on the neckline, good length, generally flattering- oh wait- those sleeves are going to get me airborne if there is a breeze. See what I mean?! Truthfully, it is just a personal preference, but if you have the same quandary as I do, maybe I can help you.
In this refashion, we'll be transforming a flutter sleeve to a gathered cap sleeve by threading a piece of elastic through the casing of the sleeve hem.
First, inspect your armpit. No, not yours, your shirt's! You're going to use your seam ripper to cut two tiny slits to thread the elastic through, so you'll want to determine the placement for those.
You don't have to mark where you're going to cut the slits; I just did so you can see where I put them.
Attach a piece of elastic to a safety pin and insert it through the tiny slit you just cut with your seamripper. If your shirt is made of a stretchy knit fabric, this will be easier. [I suggest measuring around your upper arm and cutting that exact length on the elastic. When you sew it together, it will be snug around your arm. Or just make it whatever length you want. I'm not here to micromanage you. :) ]
Sew the ends of the elastic together any way you can. It doesn't have to be pretty. Clearly.
Slide the ends up into one side of the casing so it doesn't show. If you want to be finished with this project already, you can stop here. Well, after you do the other side of course.
Otherwise, you can take a needle and thread and sew up the slits you made and keep the elastic concealed.
Repeat for the other side, and here's what we're looking at:
I like it and it only took about 15 minutes! So what do you think about flutter sleeves? Love 'em? Hate 'em? Let me know in the comments. (Hopefully I didn't alienate anyone with my feelings about flutter sleeves- haha.)