Most of the best practices I've picked up were working on existing established code bases at Match.com and TI. I work mostly with startups where you have a lot of freedom but the experience I picked up at those big companies has really stuck with me and my code is probably 10x more maintainable because of it.
I have to admit that working on a real-world software project (2 million line code base) did force me to unlearn a number of "bad habits" they taught me at university.
For example, I had to unlearn to use clever algorithms and optimized data structures. Stupidly simple code is more maintainable, because the sad but true reality is that for a dozen different reasons the next guy who will be working on it doesn't have their head in the game.
Another thing I found hard to accept was that you don't touch code that is fully functional, not even if it's horribly ugly, not even to fix that one little line of awkwardness. Ugly code that works is always better than clean code with a bug.
Most of the best practices I've picked up were working on existing established code bases at Match.com and TI. I work mostly with startups where you have a lot of freedom but the experience I picked up at those big companies has really stuck with me and my code is probably 10x more maintainable because of it.