We all sit a lot.  More than we should.  And some of us stand a lot, which can also be a bad thing over time.  Whatever the case, your hips get tight.  Over the years, I have experimented with countless stretches.  I read plenty of research from various high level fitness coaches around the world and when it comes down to it, the simplest and most basic things still work the best.  From what I have found, it all comes back around the Spiderman stretch for your hips.  It hits hits your hips in both flexion and extension and gives you the most bang for your buck.  I recommend holding 2 minutes per side daily.