How does one avoid bikeshedding in paper reading groups? We read papers once a week in my group, and I'm additionally part of a graduate class that involves reading multiple papers a week. 

I've noticed that, when asked to think about limitations or future directions one could take from this paper, I tend to focus on the minor details that I understand rather than thinking substantially about the contributions of the paper. 

It also seems to come up in group discussions, where we go off track talking about minor tangents in the paper. 

How does one avoid this for themselves? How do discussion leaders prevent this happening to groups?
This is a real problem. In a reading group I am currently a part of, we have imposed the following policy:


Before showing up to the reading group each weak, each member must write a summary of the paper, like a short review, including strengths and weaknesses as well as questions for discussion.


I think that this helps ground the discussion in reality and has avoided "bikeshedding" to some extent. Specifically, writing a summary ensures that you know where the work fits into the big picture and what its main contributions are. After this is articulated, you can be sure that whatever problems you have found with the paper are in proper context (it may then be clear that they are minor problems, not related to the paper's main contribution, or it may be that they are major objections).

I think the act of finding flaws in a paper is invaluable, whether the flaws are minor or not. So the goal should not be to not find flaws, but rather to put those flaws in their proper context.

Finally, I think a good general piece of advise is to withhold judgment until reading at least the intro and conclusion in a positive light, without skepticism. That means you understand the authors' argument before you form an opinion. It may be that the negative thing you see with the paper actually has nothing to do with what it's about.