I am a huge fan of enlisting gravity to help open my spine gently. Two great postures that do this for you are forearm scorpion (vrscikasana) and handstand scorpion (taraksvanasana, also commonly referred to as vriscikasana b). Here's a tip to help you safely get the most out of these inverted back bends. Once you're inverted, resist the temptation to bend your knees right away. Keeping the legs straight, active and strong while you enter your back bend keeps the pelvis properly aligned and tunes in lots of supporting muscles. This allows you to ease into the back bend with lots of balance and control. Push the ground away with your hands and lift the crown of your head straight up. Start to reach out behind you with your toes, keeping the legs straight. Spend at least 5 breaths there, more if you like. Then bend your knees and strongly activate the hamstrings to pull the toes in toward your head. Feel free to use a wall to play with these techniques. If you don't already practice handstands and/or forearm stands, don't start with this pose! I should note here that the exit I use in the video is not a proper exit. Don't try it on a hard surface. It feels nice on sand :)