Working on my writing portfolio.  It's vastly more challenging than that might sound.  For starters: creative, technology, academic?  What type/ styles of writing to include.  Then, how to track some of them down.  I wish I'd been more intentional in saving samples in my first four years of work.  If you are young and plan on writing, in any degree: keep samples of your work - career and personal.  As long as it is not expressly against the culture of your company, save some.  Odds are, if you ask, they will say okay.  And you will need it one day.