One method calls for using needle and thread. I used to do this, but have never been happy with it because the thread has to be inserted near the end of the tube and the fabric tends to fray and the thread’s knot would slip out half way through. When it does, I’m pretty much up a fairly undesirable type of creek without a paddle, because it’s impossible to recover from that.
The first method calls for using a bobby pin. I have not tried this method, not having ever used a bobby pin and therefore not having one. This method seems promising, though I can see that the length of the bobby pin, or rather the lack of it, can make turning the tube over the pin quite a fiddly affair.
The second method uses a tube turner, the type with a hook in the end, faces the same problem of the tube’s end fraying and letting the hook free.
The third method uses a plastic drinking straw as a DIY tube turner.
The last method calls for stitching the tube casing wrapping a length of twine or cord, then stitch across one end to anchor the cord, and then turning the tube back over the cord. A variant of that calls for anchoring the cord stitching the tube. This is better because there is less “trapped” fabric in the anchored end and hence less bulk, making turning the tube easier.
My method is a hybrid of these last two methods and the first method. I just use a length of sewing machine thread anchored to the tube’s end with a “bar tack”: reduce stitch length to almost zero (effectively making a thread bar) and zig zag near tube’s end, then pull out a length of thread:
My method does not require an extra cord like the last two methods, and does not run the risk of the tube’s end fraying and the thread pulling loose half way through the turning process.
One constant among all these methods is that if you are making tubes from woven fabric, use fairly light fabric, and cut the strips for the tube on the bias (at 45° to the fabric’s fibers) which results in more stretch in the strip, both lengthwise and crosswise, making turning the tube easier.