Stand barefoot if possible so you get a good contact with your feet and the ground. Feet a bit apart, as much as it feels comfortable to you, usually about a foot, but less will also do. Straighten up your body, let your arms hang along your body, palms inside. Close your eyes if that helps you to concentrate.
Feel energy coming up from the ground into your feet. Grow roots from your feet downwards into the ground. Think about them. How are they? Thin, thick, straight, contorted, spread out? Once you have imagined your roots start to feel them and draw up energy through them. You'll feel it in your feet and then little by little use your thought and your breathing in to draw it up through out your body and the chakras
1st chakra (genitals, pubis and a bit further up) red, 2nd chakra (lower belly up to your navel) orange, 3rd chakra (navel to diaphragm) yellow, 4th chakra (the heart) green, 5th chakra (the throat) blue, 6th chakra (third eye) indigo, 7h chakra (crown of the head) violet. If you can manage that feel the energy going out gently from the top of your head.
Your arms and hands should feel very relaxed and heavy, warming up little by little. Pull the energy up to your elbows and shoulders. If you find it difficult just imagine your blood flowing and you'll feel it ok.
Stay there, grounded for a while, as much as you like or it feels comfortable. Then, little by little start moving your fingers, your hands, feel your feet and then as last open your eyes. It is a very simple exercise and it will make you feel so much better! Try doing that when you get out of bed in the morning or anytime you feel stressed out!

You won't imagine, but I can do that sitting on my office chair as well and that works wonders!