I've had real difficulty in the past in germinating my beans. Last year though I came across a new technique to try recommended by the lovely Terry Walton on his 'Tales from Terry's Allotment' podcast. It worked a treat, so I'm using it again this year.
It's very simple - just gather up your beans into a plastic bag, along with some moist compost. Seal up the bag and store it in a warm dark place. I've put mine on top of my gas boiler in the airing cupboard.
The beans germinate really well like this and once they're sprouting, just stick them in a pot. This way you're guaranteed that every pot is a winner!