It's all about a head nod, a wink and a gentleman's agreement at the bar ... assuming you know which bar to go to.
No, it’s not really that way, at all. You must get somebody’s attention, in terms of being able to officiate. They have to see you. That is, and has always been true. Before all the clinics came about, you had to show your local D1-A (now FBS) guys that you had what it takes to work at that level. Rules knowledge. Mechanics. Judgment. If you could get those guys to invite you to - usually local - FBS spring scrimmages, you stood a chance of being noticed by the coordinator for that conference. If he liked what he saw, you might get a shot. That usually took a lot of persistence and patience. By a lot, I mean years upon years for some folks.
There is still persistence and patience involved today, but a guy that “can work” has more opportunities to get noticed by attending these big clinics. Yep, very expensive process, these days. But, a guy with skill can move up much more quickly in this system, if he is willing to make the commitment. The commitment is way more than just the desire, or even the skill. You have to be able to get away from your ‘real’ job a lot for scrimmages, spring clinics, summer clinics, etc. You need to join study groups, and spend a lot of time reviewing video. And that is BEFORE you get hired. Double that after you get hired. You have to have a family that supports you, and are willing to let you go on occasional birthdays, anniversaries, recitals, little league games, band concerts, etc. You have figure how to make up for those absences.
It takes significant effort to make those things align. But, if you can get all those things to align, it is a fun and rewarding enterprise; spiritually, psychologically, and financially. But be prepared for a lot of sacrifice.
Robert