brotha, i think most would suggest a certification to train...i personally think they are a load of shit. they teach u little to nothing. the nsca may be the exception. in any event the majority of my knowledge came from being in the gym. the other shit came from always asking questions about things i was interested in when i was in college. for instance i was just telling sumone tonight about how ammonia works for lifters and why we use it. that knowledge came from my organic chem/biochem professor. i needed to know before i started using it so i asked and we broke it down scientifically.
it may not b the easiest or the most cost effective but as far as body system maybe take a class at a local college or communtiy college Anatomy and Physiology I and II. not easy courses but extremely beneficial in understnading ur body, how it works and moves.
as far as deads ... i do sumthin for my lower back and core every day, as well as an exercise to increase my explosiveness. deads should b VIOLENT. lower back hypers, good mornings, hip thrusts, cleans, snatches, lock outs. the stronger my lower back the easier it is for me to keep 'good' form. hamstrings and rear delt exercises. and also breaking down the movement by deloading using bands and chains. rack deads as well. i have a short vid of sum reverse band deads here ...
http://youtu.be/QIVb12ovTQU
P