To develop forward bending flexibility, it is best to work on single leg forward bend, Janu Shirasana. You first stretch gently and hold for about 20-60 seconds, each side. After being able to relax in the position, you can start holding for a little longer. You can increase the stretch. Make sure the stretch is felt in the back of your leg - and you hip and back feel confortable.
Here is a slide show with different variations - mostly advanced. Let yourself become inspired: Practice makes perfect.
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