PharmCAS says to list in order of importance. In my opinion, that's pretty subjective. So, it's entirely UP to you.
Some would tell you to place the pharmacy-related ones (eg: working as a pharm tech or volunteering in a hospital pharmacy) at the top. However, I did it differently - my volunteer gig at the hospital pharmacy was, to me, less important than my other ECs. For example, I have experience as a teaching assistant and a tutor - those were placed at the top because I am proud of my teaching experiences and it was one of my main reasons for pursuing pharmacy. I ranked being a teaching assistant above tutoring because I felt that I had more of a leadership role there.
So... whatever experiences you have, just rank it however you like. There's no wrong way of doing it.