My previous question has to do with how to advance code reviews among the developers. Here I am interested in how a code review session should be carried out, so that both the reviewer and reviewed are feeling comfortable with it.

I have done some code reviews before and the experience has been very unpleasant. My previous manager would come to us --on an ad hoc basis-- and tell us to explain our code to him. Since he wasn't very familiar with the code base, whenever he would ask me to explain my code, I'd find myself spending a huge amount of time explaining the most basic structure of my code. As a result, each review would last much too long, and the process would leave both of us exhausted.

Once I was done explaining my work, he would continue by raising issues with it. Most of the issues he raised were cosmetic in nature ( e.g, don't use region for this code block, change the variable name from xxx to yyy even though the later makes even less sense, and so on). After trying this process for few rounds, we found the review session didn't derive much benefits for either of us, and we stopped.

How would you go about making each code review a natural, enjoyable, thought stimulating, bug-fixing and mutual-learning experience? Also, how frequently you do your code reviews - as soon as the code is checked in? Do you allocate a fixed time every week to do this? What are the guidelines that you follow during your code reviews?