First of all, congratulations on getting the columnist gig!
One piece of advice I would impart would be to talk with your editor to find out if there are certain expectations he or she has for your column work.
I also agree with those who say you should report with the tenacity of the best reporters out there. Just because it's your opinion doesn't mean you get to spout off about the first thing on your mind. Back up your points with facts. And for God's sake, just because it's your opinion doesn't absolve you of libel. Be as careful with your column writing as you would be reporting a crime story.
Like someone else said, don't be afraid to take a stand ... or not to take one. If you don't feel strongly about an issue after doing the reporting on it, don't force writing a column on it.
Be willing to re-examine your closely held beliefs and allow yourself to change your mind if you feel it's right. Along those lines, don't be afraid of different perspectives, but don't be a slave to them.