Code Complete by Steve McConnell : Chapter 14

In this chapter, the author provides guidelines for writing conditional statements as follows:

• Write nominal paths through the code first then the exceptions.
• Branch correctly on inequality, i.e. use $<$ and $<=$ correctly.
• Put normal case in if condition rather than in else.
  

The author then provides some guidelines in writing chains of if-then-else statements:

• Simplify complicated tests with boolean function calls
• Put the most common case first
• Make sure all the cases are covered
• If the language allows, replace the chain with other constructs such as case/switch
  

The author then provides some guidelines to write case statements:

• Order case statements sorted alphabetically or numerically
• Order cases by frequency
• Put the normal case first
• Keep actions of each case simple
• Don't use phony variables in order to use case statement
  
• Use the default clause to detect errors