How to pick the perfect Christmas tree

There's an ongoing debate at the Chronicle about when to dust off the Christmas decorations and pick out a tree. Some of us have the lights twinkling from today (December 1, others wait until a week before to give their home a Christmas spruce-up.But there's one thing we all agree on: it's damned hard work finding the perfect tree.From firs that seemed green until the needles suddenly dropped off to pungent-smelling pines that made their way straight to the top, we've all got tree horror...