There was a 60% spike in bike theft in 2015, and a 119% increase over the 5-year average
Lock according to value – frame first, then wheels; best is through both frame and back wheel to solid rack/etc.
Secondary lock should be different type from primary to require multiple theft techniques.
You want the tightest fit possible; the less room inside the chain/u-lock for tools/prying the better.
You want the lock well off the ground with the keyhole pointed down.