This silk and cashmere scarf from Chan Luu is so perfect I own two—one in black, one in blue—and they are literally the only scarves I ever wear. They’re super-warm but really lightweight, and go with literally everything I own.
They’ve also allowed even me—because I am usually no good at this type of finessing—to knot like I know what I’m doing. Here’s my personal trick, although you might find one that works better for you: first of all, but of course, make sure the scarf is in diamond, and not square, formation. Next, wrap the entire thing from one side—instead of draping the scarf over your neck and producing two halves of equal length. Wrap like you’re creating layers of a cake, and keep wrapping until there is just barely enough scarf left to knot. Then knot it low and to the side. Don’t get discouraged if you don’t get it right the first time—you don’t think those French chicks practice in front of the mirror too?