How did the Holy Spirit use Luke to gather information for his Gospel and Acts?

Of course, Luke the physician and companion of Paul was unlikely to have been the real author of this Gospel or of Acts of the Apostles, both of which were originally anonymous until attributed to him later in the second century. Luke 1:2 gives us a summary of how our 'Luke' gathered his information for the Gospel: "Even as they delivered them unto us, which from the beginning were eyewitnesses, and ministers of the Word." In other Words, the information was delivered to Luke's community ("us") in written form through a chain of writers, the earliest of which Luke believed to have been eyewitnesses.

We now know that the writings that were delivered to Luke were Mark's Gospel and the hypothetical 'Q' document (it is 'hypothetical' because we have no extant copy, although its former existence is almost universally accepted by scholars). Luke also found information in the Old Testament to be useful in writing his gospel.