I had the opportunity to shadow practicing clinicians, as well as develop and co-lead a therapy group for children, which utilized concepts from Harry Potter to help children overcome anxiety. It was really neat to be so involved on the clinical side of things and actually working with clients.
What I wish was different
I wish I'd had the opportunity to shadow more clinicians. I only shadowed two, and it would have been nice to see how others work and apply theoretical concepts.
Advice
Summer internships in clinical psychology can be hard to find, but don't give up searching! Reach out to local therapy centers in your area and see if any of them would be interested in having a summer intern.