Earlier in the week I wrote an article about the true nature of the 4-3 Defense. The way I see it, anyway. 
The 4-3 Defense has certain rules. A few years ago I wrote about the 8 Laws of The 4-3 Defense.
Block down, step down. Spill the football. 
7 Man Front. Mike Linebacker has to be a 2-gap player. 
I know a lot of people don't see the 4-3 Defense this way. That's OK for them. For me, the Miami 4-3 Defense as it was designed by Jimmy Johnson and his staff at The "U" is where it's at. 
And it is still one of the best defenses in football. So sit back and listen to How To Coach The 4-3 Defense!
Show Links

My interview with Shap Boyd on Quarters Coverage (includes the link for his video, assuming it's still available)
Download my Defensive Installation Manual
Want to learn more about the 4-3 Defense? Check out my eBook, Installing Football's 4-3 Over Defensive Front.