With regard to (1), absent any other signal, try to sit near the front of the lecture hall. You can bet the students who seek out the back rows are not the most engaged with the material.
Also gives you bonus points with the professor, simply because they can't help notice that you did that and even subconsciously getting closer signals interest. My very first exam grade when I started studying CS (25 years ago) was an "A" with a very strict professor who rarely gave anything better than a "B" on a theory-heavy (algorithms) subject - who could have known nothing at all about me, only that I seemed to actually be interested in what he had to say because I always sat in the front. I don't think the oral exam itself was responsible, because there were few hard questions, it was more a back and forth talk about things not even the core subject of the lectures. I think he would have asked more actual questions to people he thought he knew less about. So I think I already entered the exam with a significant bonus.