You don't always need to know what you want to do. At university, I tried out a few different temp jobs and hated them all until I found an office job I really enjoyed. When I got this job, I was initially nervous as I needed to speak to customers over the telephone however once I got used to it I loved the job.
I would just try out different environments. In my opinion, larger departments are better because it is busier so the time flies and you get the opportunity to meet more people. I worked in a smaller office years before and it was just me and the manager sitting in one room. I hated it because the day was so slow and it was very awkward trying to make conversations all the time. But you may perhaps prefer this rather than a bigger group.
I think I tried about 8-10 different jobs that I hated until I found the one I loved.