Discussing over miniscule details of the project which leads to a situation where no progress is made due to the time consuming nature of the discussion.
If you use software programming patterns a lot without thinking about whether you should use them, you're probably creating code smells. Best practices become worse and worse when they're used just for their ends in themselves.
There's the boy scout rule1 for code refactorings: always leave the code in a better condition than you found it in.
Copying and pasting makes your code really, really wet.