Next time you're counting sheep to no avail, try sticking one foot outside the covers.
According to the above video from Science of Us, studies have shown that a higher internal body temperature makes people more alert and awake—and that the opposite is also true. Just before drifting off, our bodies automatically cool down. But if sleeping still isn't coming naturally to you, you can actively lower your body temperature by keeping one foot cover-free. It works because feet (and hands) contain vascular structures designed to dissipate body heat. These blood vessels provide blood to the veins under the surface of the skin, and when the skin there is cooled down, the blood also gets colder. When that blood circulates, your core temperature lowers—and you're dreaming in no time.