it is by no means a topic that I have "mastered" by any means... but there are a few things that i try to keep in mind.
one of them is the quote:
if you hear hoofbeats, think horses, not zebras.
this quote is supposed to remind people that common things are common.
But db reminds me that premature closure is also a problem.
So I would revise the old saying thusly:
If you hear hoofbeats, think horses, not zebras. unless you're in a savannah and you see stripes.