One of the most advanced postures is a back bend called urdhava danurasa. The literal translation of this is Upward Facing Bow Posture, though many people also call it the Wheel Pose. I prefer to use the literal name, since it evokes the true tone of the pose: the dynamic suspension of a bow about to set an arrow into flight. It's an exciting, breathtaking pose, but it's one that must be done carefully.
If you've been practicing yoga regularly for some time now, you may be ready to give it a try. But if you're new to yoga, I recommend you begin with Bridge Pose. Begin by lying on your back. Place your feet flat on the floor, hip-width apart and parallel, with your knees up and pointing to the ceiling. Leave your arms down by your sides, then press your weight into your feet and lift your hips into the air. Interlace your fingers underneath your hips and wriggle your arms towards each other so that you stretch your chest. Hold for 5–15 breaths, rest, and repeat 3 times.
Right now you'll be feeling one of two things: energized and stretched, or itching for more of a challenge. If you are ready for something more difficult, give Upward Bow, or Wheel Pose, a try. Begin by doing the Bridge Pose and once your hips are in the air, place your hands under your shoulders with your fingers pointing toward your feet. Keep your hips lifted and slowly and gently press into your hands until you can place the top of your head onto the floor.
Rest here for a moment. Make sure your hands are no wider than shoulder-distance apart. Your fingers should be pointing back at your feet. Be sure to draw your elbows in so they are no wider than your shouldersthis is the hardest part, and the part that most people fail to do. If you're lazy and you skip this step, you can cause serious injury to your shoulders and back.
From there you may try to push yourself up fully. But listen to your body. If you aren't able to put that sort of pressure on your arms and back, don't push it; go back to Bridge, practice lots of Downward Dogs and other shoulder stretches, and try again in a few weeks.
Please feel free to email me your questions on this oneit's one of the more confusing postures. Back bends are invigorating and full of different health benefits, but remember to practice them at your own pace.