Visible Time Code
Always ask for working copies of the movie that you score that contain a visible time code in the video.
So many things can go wrong regarding the sync of music and movie (e.g. wrong framerates, weird video codec glitches etc.) that you should not leave any chances for them to happen unnoticed. Once your scoring software timecode and the timecode printed on the video are in sync (also still at the end of the video) chances are good that actually everything is running at the correct speed and correct frame rate and you can start composing.