Just playing more, consciously making the effort to use the pinky, will be the best but specifically do more pinky related stuff... like 3rd-4th (pinky) finger trills. Another exercise I used to recommend to students was to practice scales over-the-neck. In the traditional under-the-neck position, the first (index) finger is the anchor/pivot point of strength. Over-the-neck, the pinky becomes the anchor.