Software reviews may be divided into three categories: "Formality" identifies the degree to which an activity is governed by agreed (written) rules.
Informal reviews may often be unnecessarily expensive (because of time-wasting through lack of focus) and frequently provide a sense of security which is quite unjustified by the relatively small number of real defects found and repaired.
IEEE 1028 defines a common set of activities for "formal" reviews (with some variations, especially for software audit).
The stipulated sequence of standard activities is largely based on the software inspection process originally developed at IBM by Michael Fagan.
As a general principle, the earlier a technical document is produced, the greater will be the impact of its defects on any downstream activities and their work products.