...
Beyond the code author, there is an inherent responsibility of domain owners to ensure that the code review objectives are met prior to giving approval. Also, do not forget the Sibros' steps to writing quality software.
Requirements assessment and updating or adding appropriate requirement
Did we really build what we wanted?
Have the requirements been updated?
Review design and API interface
Is the header file or class interfaces correct?
Is there any possible memory leak or an awkward code interface?
Review the code
Stylistic changes should not be the focus, although you should point that out
Does the code address the requirements?
Is the code expressive and otherwise follows the coding standards?
Review the unit-test code
Do the tests hit the requirement?
Do they leave a quality barrier behind in case someone alters the API interface being added?
...