Damon Lindelof and Carlton Cuse revealed in this recap that the reason that some survivors were transported to 1977 and others remained in the present was because they were unable to exactly replicate the conditions of Flight 815 aboard Flight 316. Minor differences caused the survivors to successfully crash on the Island, but not exactly as they had planned.
Benjamin Linus's intentions when he met Locke off-Island are more explicitly detailed. Ben did not want to lose his role as "leader" of the Others, and by manipulating and killing Locke, he could possibly regain his position. He first listened to Locke in order to gain information about Eloise Hawking and the Oceanic Six in order to know how to return after killing him.
Damon Lindelof and Carlton Cuse revealed that the radio broadcastHurley and Sayid received on the beach in "Il lupo" was due to time travel from the 1940s and was not being broadcast live.
Damon and Carlton also confirmed that when Locke, Sawyer, Juliet, etc were flashing through time, every flash was to a "significant" point in time of the island's history.