Hopefully, if the snowdrops are growing well, a dormant single-nosed bulb planted in the autumn will produce an offset in the next growing season. This offset, if left undisturbed should then grow into a fully sized bulb the following growing season.
Examples of mature bulbs with an offset
Clumps of snowdrops require regular lifting in order to split up and divide the bulbs, so giving them the space that they need. Regular lifting, preferably every two or three years is also a good way to keep a check on the health of the bulbs, allowing the early removal of any diseased or damaged bulbs.
Dividing the clumps can either be performed when the bulbs are dormant or in full growth. On lifting the clump some offsets will naturally detach themselves from the parent bulb or they can be removed with a little help. Never pull off the offset as this can cause damage to the basal plate. Gently tease the bulb and offset apart and cut through the basal plate with a sterilised scalpel (one dipped in meths is ideal), dust the wound on the parent bulb and offset with yellow sulphur powder. Occasionally strong growing snowdrops, as in the case of some elwesii will produce a ring of offsets which completely encircle the bulb. In this case I would remove the offsets; if left to grow unhindered they can squeeze the parent bulb so much that it will not survive.
If dividing a clump while still in growth then extra care will be needed so as not to damage the soft bulb or break off any of the roots. The clump will be easier to handle if all the soil is washed off first. Try not to leave the bulbs out of the ground for any length of time to avoid the roots from drying out.