"Being liked [ or not ]" in the first 30 seconds of a class can seem intimidating. I have felt anxiety in the past, trying to be sure to put my best foot forward and letting my class see not only the best in me, but also the relevance of what they are about to learn. I have changed my outlook on that somewhat as time has passed: while I still put an effort toward those first important moments, I have tried to be particularly careful to be sincere and set a solid groundwork for future areas that the students will compare me against later. Some students know that first impressions appear stilted or staged if I look like I'm trying too hard to gain their approval early. If I am sincere, than I will always have that to fall back on as the course progresses.