I've made a bunch of these!
Fold a square washcloth in half so you have a rectangle. Start at one corner away from the folded side, single crocheting along the open side toward the fold. A pin now comes in handy to hold the fold while you turn the corner (do 3 stitches all in the same spot to turn the corner) and crochet toward the pin. Another corner there. Now comes the "tricky" part! Bring the next "side" up to meet the place of beginning. You now have 3 corners of the washcloth together. This will give you a fold created by your crochet work. Again a pin will help to hold that fold until you get that side done. Work to the corner where you piled those 3 corners together. When you get to that intersection, you'll see how the last corner needs to come up to the beginning so now all 4 corners are together. If you want these plain, pull in the ends of the thread and you are done. If you want them fancy, double crochet now around and make a loop to hang them.
I have sometimes reserved the 3rd stitch in the corner to put into the next fold. Experiment a bit with that to see what helps you the most. Hope this is clearer then mud and helps you!