The biggest misconception about backbends is that you need a flexible back in order to do poses such as Urdhva Dhanurasana (Upward Bow Pose) or Ustrasana (Camel Pose). Yes, you do need some mobility in your back, but the entire front body and shoulders can make or break a backbend. With consistent practice, you will find that your backbends will be deeper and easier to perform.
As with any asana, take backbends slowly, and never force your body into postures. Start off your practice with a few rounds of Surya Namaskar (Sun Salutations), then try these 7 poses to fire up your entire front body and shoulders. Make sure to keep your abdominals engaged and more importantly, make sure to breathe!