One of the most common operations in the development of a project that makes use of a version control system, is that of reviewing the differences between the local copy of a given file in the working area, and the last version of the same file stored in the repository.
Using a graphical comparison tool for this operation may help greatly to perform this task. A tool of this kind will show both versions of the file side-by-side, highlighting the lines that have been added, deleted of modified.
This post explains how to do this and other similar operations in a project that uses git as version control system.