The rule "Avoid parentheses when methods take no arguments" is part of the Ruby style guide. It suggests that when a method takes no arguments, you should not use parentheses. This is because the use of parentheses in such a case is redundant and unnecessary, and it can make your code more difficult to read and understand.

This rule is important because it promotes cleaner, more readable code. In Ruby, clean and readable code is highly valued. By following this rule, you can ensure your code is easier to understand and maintain, which is crucial for long-term project success.

To adhere to this rule, remove the parentheses when calling a method that does not require any arguments. For example, instead of writing 'test'.upcase(), you should write 'test'.upcase. Similarly, instead of Kernel.exit!(), write Kernel.exit!. However, note that there is an exception for super - super by itself is different from super(), so in this case, parentheses may be necessary.