Colossians 4:5 – 6
New International Version (NIV)
5 Be wise in the way you act toward outsiders; make the most of every opportunity. 6 Let your conversation be always full of grace, seasoned with salt, so that you may know how to answer everyone.
From BibleGateway.com: http://www.biblegateway.com/passage/?search=colossians+4.5-6&version=NIV