I really wish I could tell you the formula. I really do. The bottom line is - it's incredibly subjective who gets hired and who doesn't. There are LOTS of good officials out there. You have to be in the right place at the right time and there needs to be an opening in your position that you work for them to hire you (some guys switch positions). Then, the coordinator has to like you enough to hire you. Additionally, supervisors need to have more diversity in their staff. So if you're a woman or minority, you have a little bit of an inside track to get hired.
I know there are officials I used to work with in D2 and D3 that can work at the level I'm at. It's just TOUGH to break in. Some guys get lucky though.
You can gain a huge edge on everyone else if you're 1) young and 2) in VERY GOOD physical shape. Coordinators love hiring guys that "look good in the uniform". Sometimes the officiating is secondary to that fact. haha.
Now, another factor, is that supervisors won't hire you unless they see you work in person. So the only place they can see you work is at their clinics, which are anywhere between $800 and $1500 a pop, not including travel and sometimes lodging. Most guys don't get hired out of their first clinic, so you'll be looking to drop that much money per season on clinics until you get hired.
On top of that, you never know where you stand. So you keep going to these clinics and you don't know if you're next in line or if you're 20th. So then you ask yourself how many more clinics and how much more money do I have to invest to get a shot? Or, if you're kind of in with two different conferences or consortiums, then you have to play the balancing act, or worse, choose one. Then you think, did you choose the right one? Again, you didn't know your spot in line, so you could have quit the conference that you had the best chance to get hired with. My advice in this scenario is to ride the fence as long as you can.
It always helps to have a "horse". Someone with some pull that likes you and can get in the coordinator's ear to give you a shot.
The most important thing is to not measure your self worth as an official by the level you work. There are good officials at every level. Don't be discouraged if you never make it to D1. Again, it's tough. But, you can be a kickass D2 or D3 official who is highly respected in your area, work NCAA playoffs every year, and that's something to be proud of! Always enjoy the level you're at. If you move up, then it's icing on the cake. Don't let my advice discourage you if that's your goal is to be D1. You just have to put in the effort.