The best answer is: Stretch the muscles you will be working out.
While stretching can be a part of a warm-up routine, it is not considered a weight-lifting warm-up technique in the same way that the other options (jogging, knee bends, and performing planned moves without weights) actively prepare the muscles and joints for the specific movements required in weight lifting. Stretching is often recommended after a workout rather than as a primary warm-up activity.