With great difficulty - try living with them :-)

You could try an iron phosphate based bait, Cjc, if they really are snails. If they are immobile, and fixed to the leaves, they might be scale insects, instead. If so, I have had the best luck getting rid of them by immersing the entire plant in a solution of carbaryl (Sevin) mixed with a non-ionic surfactant. Organic remedies include touching each scale with an alcohol soaked cotton swab, but they are too good at hiding in the bases of the leaves to make that really practical.