There's no single best answer to this.
Students can stand out in dozens of ways.
But ultimately we want to see students who have mastered specific skills. Grades are important - but are only one piece of the equation. You need to show that you've developed skills that are transferable to the workplace. You can develop them in the classroom, through campus clubs and activities, or in any element of your life. Regardless of where you cultivate them, the key is to master these skills, be able to point to how you have applied them, and explain how they will help you in a specific job role.