Oh my! So many come to mind, but since we're going super broad, here's an oldie but goodie - "begin with the end in mind." In his book "The 7 Habits of Highly Effective People," Stephen Covey writes "If your ladder is not leaning against the right wall, every step you take gets you to the wrong place faster." From a marketing perspective, we can apply this principle - Covey's "Habit 2" - in so many ways. For example, I've seen hours and hours of planning - and at times configuration and testing - go to waste because the people involved were so focused on solving at a micro level, they forgot to consider the big picture at all. I'm by no means a master of this habit, however, from my experiences I do try to always start any planning with the question "how will we measure success?" and let it flow from there.
Great discussion, Shane LaBounty!