What do you feel is the key to promoting in the secondary zone, aka "first look" (all branches/ranks)?

Seth Godin's book, Linchpin: Are you indispensable? may be the best way to get that elusive selection for promotion. If someone is an SME in one particular area, then use it to the best of your ability. Take for instance the story of USMC Gunnery Sergeant John Basilone. He was presented the Medal of Honor for his actions at Guadalcanal due to his expertise with machine guns. The series, The Pacific, has a great replication of his deeds of keeping a Japanese regiment of 3,000 out of his AO. Obviously, becoming the EXPERT in something that is relevant to the military will get you that well-deserved promotion

Just for entertainment over the years, I read the bio of General Officers/Flag Officers with whom I came in contact. Mostly because they were part of my chain of command or my customer's chain of command. In almost all cases, I could spot the point in their career where they took a direction that made them destine for a star. Most were promoted at least once "below the zone." Common turning points were assignments to challenging or special duties such as Service or DoD budget office or aide to a General Officer, assignment to a high profile special project or unit, such as Arms Limitation Talks military staff, or command in a high profile unit, such as the 89th Air Wing (presidential support) or Old Guard in Military District Washington. In most cases they also attended Professional Military Education schools in residence. They all had one or more advanced degrees, usually paid for by the Service (AFIT in the Air Force). They were expert communicators and made their subordinates believe they were important to them (great people skills).
The keys based on my observation:
-Take the hard jobs and do them well
-Take advantage of opportunities for professional military education and advanced academic education
-Work on being a great communicator
-Take care of people

I was just selected on my 1st look for SFC. I have no special duty assignments (drill, recruiter, AIT PLT SGT, etc). What I do have is 5 degrees including a MBA. I'm not sure if that's what made me a part of the 22 that were selected at of 974, but I feel as it played a large part.