Dive and film as much as you possibly can. Edit & review to improve your skills and then do it all again! Nothing substitutes for practise. I've never done it but working as a resort pro for at least a couple of years is probably the best training you could wish for.
Listen and learn from everyone and then find out what works best for you. There are lots of approaches and methods to experiment with.
Don't confuse 'gearheads' with very little practical ability to people who really know what they are talking about! Basically always look at someone's work before you take what they say for granted...
There are very few people in the world who make their entire living from filming underwater exclusively for broadcast. Most will have some form of supplemental income from other types of filming or from other types of work/businesses.
Oh and don't forget to have an amazing life doing what you love!!
- ScubaBob likes this