Biological washing powder/liquid in some warm water and gently rub from the edge of the stain inwards. Once the stain has gone do it again with clean water and then cover with a clean towel and tread on it to absorb as much of the water as you can.
Just tripped on the stairs carrying a mug of tomato soup. It's gone everywhere! Have got it off the walls and banisters. The carpet however. . Any ideas? Have soaked it in water and mopped it up with a towel but not looking good.