I disagree with Tinkerbell slightly. My strategy last year was to be concise with descriptions of EC's of lesser importance and more obvious substance, and write detailed, long, descriptions of my most significant experiences. I wouldn't BS through 500 characters about my involvement as, say, a volunteer builder for Habitat for Humanity. But I'd use the full space to describe a leadership position or a research experience. I think that long descriptions about lesser EC's serve only to draw the eye away from more the more important experiences and to call into question the big claims you make about the significance of your key experiences.