Imho, there is only one thing really important when you write software: readability.
Software is written once. And then fixed, improved, upgraded, fixed again a few times. Each lines gets written 1-10 times during its lifetime. But those same lines get read hundreds, if not thousands of times. Before you can write additional code, or fix bugs, you need to read the existing code. Sometimes that is your own code, usually it is someone else's code. Coming up with good solutions, and implementing them, takes a lot of time. But reading and understanding someone elses code takes an aweful lot more time. And often, it will not be trivial to understand your own code that you wrote 5 years earlier.
So anything you do when writing code, readability is the most important factor, imho. Documentation, comments, even picking function-names and variable-names. Even the wrong coding-style can make code unreadable. Picking the right language is a factor too. That's why assembly is hardly ever the best solution.
For the same reason, many of those fancy new languages are useless too. Because most people don't know them. Or because people use heaploads of libraries that you need to plough through before you understand what it does. C++ and Java are OK, because they are well known. Perl is an example of a shitty language, even though well known. Because writing a function takes 1 minute, understanding one function takes an hour.
All those new fancy languages you learned at university ? 99% Of them will not be used. Not in real projects. Not in large projects. Not in projects that have multiple people working in them. Not in projects for software that will stay around for a decade.