Start/get/keep the ball rolling

To start or get the ball rolling means to get something started, to initiate a discussion, a project, etc. To keep the ball rolling is to prolong whatever has been started. The figurative use of these expressions is originally American and dates from the mid-19th century. They all derive from earlier, literal usages, during the late 18th century, in any number of sports where a ball was put in play to start proceedings.