So far we have a few useful principles to follow during web and generally software development. Everyone remembers the DRY, KISS and all that. Let me add my own little gem to the list. It's called MY and focuses on modern or old source control. It's so obvious that I'm sure you already aware of it. So here it goes:
MY: Merge Yours!
Basically it means that if you collaborate in a process, you the developer is responsible for other people's work; you have to respect others work, no matters how a piece of junk is that. So when you start working on someone else's code, first merge yours. Merge your code with poor Jane or John Doe's stuff before you push. Obvious no? Then do it.
Its all about respect, no coding required.
I'd like to invent an other nice principle abbreviated ASS so I'd wear a T with "KISS MY DRY ASS" on it.