If you are refereeing or listening to a presentation or giving a presentation:1. Make sure your first sentence gives the essence of the paper. Maybe you need a second sentence, but not more. If you are speaking, surely in the first two minutes.
2. Think of your questions or comments or advice as ways of making the paper better. You may have some other questions as well. But your main purpose is to help the scholar do a better job. (That is not what is usually done in questioning, but this “make the paper better” strategy is a real winner.) It is not easy to say how to make the paper better, but you will find that you will be respected and trusted for doing that. If there is a flaw or a deep problem, suggest how to fix it. If you feel that your paper is crucial, in refereeing you do not want to say that. Rather be substantive--"earlier work has made similar points, and it needs to be referred to" or "these ideas have a history in the literature, and the paper would be more credible were that history referred to."
As for myself, when I am reading a paper or listening to a presentation, I am very actively trying to figure out what is the main point, the deeper issue. When someone expects me to wait for 45 minutes to their getting to that main point, I find that intolerable. If I am unsure, I ask a question in the first 15 minutes trying to be sure I know what’s up. If I am reading a paper, I’ll go to the end or wherever to find out what’s the point. Others, more methodologically sophisticated than I am, or closer to the subject, will find more detailed issues, by the way.