Ceremonies and Rituals
Ceremonies are custom tailored sets of actions, usually for a one-time purpose. A ceremony is often based on instructions Druids get in the Otherworld, from their allies when journeying about a problem. In their journey, Druids learn about the root cause of a problem, and sometimes that a ceremony needs to be done to resolve the issue. The Druid might get clear instructions right away, or might have to go on subsequent journeys specifically designed to find out about the where, when, and how of the ceremony.
Alternatively, someone could request a ceremony from the Druid. He or she still goes on a journey to get details, but the purpose of the ceremony (e.g. a wedding) is clear from the beginning.
Often, the general circumstances under which a ceremony is to be held play an important role. That can be the quality of light (dawn, day, dusk, night,) a specific day or time period (Beltane (May Day,) under a New Moon, in fall) and a certain place (the forest, on a river bank, in a specific stone circle.) Even special weather situations (e.g. fog) could be necessary, requiring some flexibility from Druid and client.
Rituals are repetitive actions that help once they have been done over a period of time. Their power lies in the repetition, as long as they are done purposefully and in full awareness of the meaning.