When talking about effective programming and style guides you can’t list every dumb thing you shouldn’t do, but I think you can follow some higher level principles.
For example, my first advice would be “Don’t be clever”. Being clever leads to highly un-maintainable and potentially dangerous constructs. It is often tempting, to surprise yourself and your colleagues, with clever code. Unless you are Linus Torvalds, please don’t. Developers have a fine tuned part of the brain that is optimized to copy and paste the unsafe and poorly documented patterns, so please don’t encourage this behavior. For more details about why being clever is bad you can check out my Don’t be clever article.
Now, if you are too clever you soon slide towards my next advice: “Don’t be stupid”. Usually, if you are too clever, you end up doing stupid things. Of course, you can also do stupid things if you are simply stupid, but at the end of the day it’s all the same thing. And if you are stupid, then please, I beg you, follow my initial advice: Don’t be clever. Notice the vicious circle here? I think that in order to have a sustainable code base we should all stop living in this vicious circle and be reasonable.