In reading over students' discussion of others' work, I have some suggestions that may be more generally useful.
2. The same for the questions you may ask at a seminar. You may be thinking "out loud" as you write the questions, but after doing that, underline the main question or questions. They need to be sharp and not very long. You can put all he context and qualifiers after the questions, or rescue the main question from the middle of your question paragraph.
3. What this all says is that you want to examine your work for the main points. So if you have written a paper, you want to then write an introduction that says the main ideas in a sensible way. Put differently, could a busy person get your points by reading the first sentence of your section or paragraph, etc. Is the introductory two pages sufficient for them to figure out your conclusions etc.
What you want to do is not point what's wrong with work, so much as figure out what the speaker should do next. Or even better, what should be her main contribution? (If the paper is truly vulnerable, think about how to make it stronger.)
One other point. At the recent Health Economists conference here in June, there was an opening session of Peter Orszag and Casey Mulligan. Mulligan had just launched a book on how the responses to the Great Recession actually harmed economic growth. Orszag said that if we want to get at the 1/3 of health expenditures that are wasted we needed not only deal with supply, we'd have to deal with insurance. Very different approaches: Mulligan examined things as a first-rate economist. Orszag examined things in terms of what you needed to do to tackle a big problem. Neither was much moved by the other--since Mulligan is concerned with getting the numbers right, and Orszag was concerned about transformative change and politics. They were not talking past each other, they were talking about different things.