A great trainer has "the gift." What is that? Well, those who have it know...those who don't, well, don't!
Not trying to sound cocky in the least...it's just that it's so evident these days in our industry who's actually in it because their heart's in it. Clients can see this. It's something that can't be faked, bought, or taught. A great trainer walks their talk. They eat, breathe, live, and love health and fitness. A great trainer spends a majority of their free time getting their hands on as much fitness-related info as possible, to expand their horizons and better serve their clients.
A great trainer doesn't have to TRY to be great.