Disclaimer: I have personally never applied for a clerkship or a law firm job, but I do know many people who have been successful
Any experience or activity on your resume that shows you have other, non-law-related skills which may be valuable to a law firm will help. (For example, a successful exchange may show that you are an independent worker and have excellent time management skills etc.)
Like lynt.br said, it will also give you something to talk about. A lot of law firm clerkship interviews will ask behavioural/situational questions like "Tell us about a time when you had to organise something to a tight deadline" and if you have a variety of interesting experiences to draw on (I'm sure interviewers are sick to death of the "oh yeah I had to prepare for a moot with a tight deadline!!!" stories), that will obviously improve your answers greatly.
However, most law firms which offer clerkships will have GPA cut-offs. There's no point having all these great experiences to talk about in the interview if you don't make it to an interview in the first place. Therefore, your first priority should be to make your grades as high as possible. Having extra- and co-curriculars is great but don't let it negatively impact on your GPA.