Push ur teamates to perform without being obnoxious first of all. A lot of rowers get resentful since coxswains dont usually do the workouts. if u really want ur rowers to respect u, do their workouts with them.
Secondly, steer the boat straight. I know this sounds obvious, and I know its not that easy, but it a coxswain's most important job, in fact the reason they are there, so doing it well is a big plus.
Third, no matter how long you cox for, you will not understand the technique involved in a rower's stroke. The coaches do, and give tips to the rowers on how to improve it. This is not your job though.
Finally, just make sure you have a good time with your rowers. In my experience the fastest boats are ones filled with respect, admiration and friendship, not just muscle. Rowing can really be a great sport, I hope you have a great time!