Coding Guidelines

These are some of the guidelines it is useful to follow for more readability and maintainability.

Indentation: Always start at the first column for your #include statements and the main and the brace which indicates the beginning of the statements in main. Then, indent the local parameter declarations by a tab or 2-4 spaces. Leave a line empty after the declarations and then start the actual code. Similarly indent by a tab or 2-4 spaces for every control statement such as if, while, for, do. See the Example Program
Line length: Do not exceed a line length of 79 columns. This is important for readability since wrapped-around lines clutter the file and certainly a print-out loses the information.
Preprocessor Directives: At the beginning of every .h file of yours, please add the preprocessor directives as specified below at the beginning and end of the file. This is useful to prevent the error of multiple definitions if your .h file is included in multiple .c files. For e.g., if the file is name my.h, then:
#ifndef __MY_H
#define __MY_H
At the end of the file, add the following:
#endif /* __MY_H */
Meaningful file, function and variable names: Please name the files, functions within the program and the variables with meaningful names that make apparent their use. Of course, you can use i, j, k etc. for indices and n, size etc. for maximum values. Other than that, try to name the variables without their being excessively long while conveying their use. Typical codelines (in industry or open source) prefer that any pointer variable must start with p - for e.g., pnode and a double pointer as ppnode. It is also useful to use typedef to name your own data types instead of using struct node etc. Whereever there are a known range of possible values that are possible for a variable, use an enumerated data type by the use of enum.
Compilation Directives: Always use the following command at the minimum while compiling your code: gcc -Wall and ensure that there are no warnings when your code is compiled. This helps you in catching lots of difficult run-time errors during compilation time itself and save you lots of heartache.

For more articles on coding guidelines, see the links below: