I am currently in a Civil Clinic at a T2 school. There is a seminar component that goes through the various stages of litigation through simulations from Client Interviewing to seemingly conducting a trial. We also staff various sorts of cases for people who cannot afford representation (i.e., landlord tenant law, employment discrimination, equity skimming on houses, unemployment compensation, etc.). Once the clinic votes to take on a client, one or two of us students are put on the case under a faculty supervisor. The responsibilities on any given case vary quite a bit. You might pick up the case at the appellate level, hearing stage, fact investigation, discovery, etc. The goal of the clinic is to allow each of us to at least conduct a mini-trial in an unemployment compensation appeal.
Another interesting aspect of the Civil Clinic, completely unrelated to civil suits, is that some of us have been given the opportunity to work on policy/legislative projects with groups in Washington D.C.
Overall, I would say the clinic is an awesome experience and lets you see the more practical side to practicing law enabling you to bridge the gap between law school and practice much easier. The clinic I am in only has generally up to 10 slots, with 3Ls and those who have not done a clinic before getting preference. We had to list our GPA, however, not sure how much that plays a role in the selection process. The clinic I am in is 6 credits and requires a significant amount of work; therefore, time management is really essential if partaking in a clinic.
Other clinics offered at my school: public defender, mediation, post-conviction, technology venture services, indian legal clinic, patent law clinic, criminal practice.