All snowdrops prefer cool, moist conditions in the spring and a surprisingly dry summer dormancy in the shade. Dig a deep but narrow planting hole probably 4-6" deep (an asparagus trowel is a great implement for the job) loosening the soil at depth and introduce your snowdrop into this at a depth slightly greater than it was previously planted (where the stem turns green!) Firm in and water the soil remembering to label the spot. If planting more than one of the same variety, plant the next about 4" away ideally. They will clump up in time.
Galanthus images courtesy of Janet Lecore, Mark Smyth, Matt Bishop, Eddie Roberts and Chris Ireland-Jones.