Certified instructors here in AR are part of the Grand Lodge's program for preserving and perpetuating the adopted ritual. Certification is based on passing a pretty rigorous exam by one of the senior instructors, who certifies to the Grand Lecturer and the Grand Master that you've got your stuff wound down really, really tight, at which time the brother is awarded a card, commissioning him to teach that part of the work for which he has ben found proficient. Word-perfect, with no un-self-corrected errors is the standard, plus the floor work, etc. Instructors are certified at one of three levels, Certified Lecturer (white card, to teach the proficiency lectures for each degree), Certified Instructor, 2nd Section Master's Degree (red card, for the MM 2nd Section), and Certified Instructor (blue card, which includes all parts of the adopted ritual with the exception of the MM 2nd Section). The Grand Lodge also offers a Lodge Officer's Proficiency certification (white card) as an incentive and check for officers, covering all parts and floor work in opening and closing the lodge on all three degrees, and dispensing and resuming labor. Certification is good for 4 years, at which time you must be re-examined. The expectation is that each lodge should have at least one certified instructor, a handful of certified lecturers, and that the three principal officers ought to have an officer's proficiency card. The reality falls way, way, way short of that goal.
The GL of Arkansas' Digest of Laws calls for the election of a Grand Lecturer, and the appointment of seven area Deputy Grand Lecturers, who would serve as a board of custodians for the work, with each DGL responsible for schools and all instruction in his assigned area. Each DGL is authorized to have a District Instructor and Deputy District Instructor for each district in his area, to help spread the load among the many lodges out there. That's what the Digest says, anyway... About 15 years ago, they quit designating the Deputy GLs, and the entire burden has pretty much fallen entirely on the Grand Lecturer to carry on the certification and schools program, as well as being the sole authority or custodian of the Work. So what we've had since that time has been a series of exemplification schools every other month or so, along with a grand exemplification of the work on the day before the Grand Lodge opens its annual meeting. And the number of certified brethren has steadily declined, as the old guys get older, and not many new guys step up to learn the work, at least to the level needed to be certified. Altogether, among ~ 15,000 Masons, we have only about 160 or so cards in effect at all levels, most of these being the officer proficiency and lecturer level. They issue and renew somewhere around 40 cards (total - all types) per year over the past ten years or so. So, there aren't very many certified instructors out there.
Fast forward to May, 2015: when our Grand Lecturer suffered a massive heart attack and died, quite unexpectedly. Since there were no other official custodians, and a busy schedule of schools coming up, the Grand Lodge had a problem on their hands. Fortunately, they're in the process of "putting the Board back together," starting at least with the seven DGLs, and as they can assemble enough red+blue card holders, working at trying to re-establish a network of district instructors to come back to what the Digest originally called for, and to re-boot ritual instruction though the grand jurisdiction.
As an instructor, I teach the adopted ritual... what the "right words" are, and how to use them. I also do a big chunk of our lecturing for our candidates, and as we work through the lectures, it helps to explain - in "education mode" - just what each phrase means, so that the guys are not just repeating words and phrases like a parakeet ;-) ... and I often wind up delivering the second and third sections of the degrees (including the 3rd section of the Masters), where the symbology and practical lessons start to come out...
So, if you're going to work as an instructor, get your certifications in the Work (the cards lend credibility, at least), get intimately familiar with all the work in the Monitor, and practice, practice, practice. Each and every time, practice giving the work the same as if you were giving it in a degree or exemplification. I drill myself harder than my students to keep things churning in my memory, and we have a small group of four or five guys in my area as sort of a Ritual club to work with each other and keep each other sharp. Attend as many grand lodge schools as your cable tow will allow, and travel to as many degrees as you can. You may rarely get to confer one or be King Solomon, but it keeps the Work going over in your memory, and you can discretely help your other brothers learn their parts. It's a lot of work, but a lot of fun, and something our district and neighbors need real badly these days.