Switching Lines of Service

I am going to be starting big 4 audit in the northeast this coming fall. I didnt have the chance to apply to the TAS department as I had originally wanted as I went through ocr and their were no postings for TAS. I know it would not make any sense to try to transfer lines of service too early on at the firm but I do want to make the switch eventually. With this in mind, what is the best route to go? Should I start networking right away with people in the TAS group and make my motivation known to my mentors/other superiors? Or, should I fly under the radar for a year or so, get good reviews, and then try to switch? I am just kind of confused about how to tackle this issue, and even though I have a lot of time until I start I would like to have a game plan in mind. Would really appreciate some help on this.