There's two things that make a successful personal trainer, in my opinion. Having a great physique and enjoying the job. When you love exercise, training, hard work and discipline, and you make the sessions challenging and fun, people will love it.
With your physique, you are your own walking billboard, no one's going to pay to train with a fatso or a skinny guy. An athletic physique is more attractive to the average person than a muscle bound tank imo, because they can be a little intimidating to the avg person, and most clients are women who want to lose weight and tone up. Don't expect a lot of male clients who want to bulk. Though I have a female powerlifter as a client, she loves deadlifts and heavy bench! Very satisfying to train.
Imo having good technique and instruction is obviously benefitial, but I've seen some techniqually crap trainers (they don't know what a kinetic chain is) be really sucessful because they have a great attitude, they make the training sessions challenging and fun, and they make the person sweat.