I haven't had my hair curled with rags since I was a kid, but one of my internet friends, Kathy, was kind enough to share her method with me---and I'll include a few other methods I plan to try below as well!
Here's Kathy's Step-by-Step How-To on "Rag Curls"
Step 1:Cut up an old t-shirt into 1-2inch wide strips. They don't have to be even, but they should be all about the same size. Make the strips as long as you can. If they're too short (you run out while you're twisting them up) you can tie two together.
Step 2:The hair should be nearly dry. It can't be completely dry, nor should it be too damp. Take a section of hair. For this tutorial I did my whole head in 4 sections for somewhat loose curls, other nights I have done 6 sections. Remember: the larger the section, the more straight hair you'll have at the top of each curl, so if you want curls to start at your scalp, make more sections---and if your hair is a little too wet, larger sections won't dry completely overnight, so go small.
Smooth out the section of hair and wrap it tightly around the rag. I hold the other end of the rag in my teeth to keep it from pulling out. Then, wrap the rag back up the hair in the same direction that you wrapped the hair. (If you go the opposite way, it untwists the hair, so you'll know if you're doing it wrong.)
Step 4:When you get to the top, take the other end of the rag out of your mouth and tie the two ends together in a knot.
Step 5:Start the next section. Twist it in the same direction as the first (i.e. all counter clockwise or all clockwise.) Continue all over your head. When you get done, it will look like this.
I usually do this right before bed and sleep on it. But it will make your hair at least wavy within a couple hours.
In the morning, begin by undoing the last knot that you tied. Take the rags out in the opposite order that you put them in. Unravel the rag, then gently pull the rag straight down. The ringlet will loosen and release the rag.
Separate a small section of hair from the ringlet and twist it around your finger to shape a curl. Repeat for the entire ringlet. Continue to undo the ringlets and shape curls. Finger comb curls to relax and separate them. Style as desired.
Thank you Kathy for sharing this great tutorial! Here are my other favorite no-heat methods to achieve curls:
You can also read Andi's blog post about no-heat curls here.