Using a diverse range of rep ranges rather than trying to aim for 12 to 15 reps per set. Don't get me wrong, I added some decent size in a relatively short time with the higher rep stuff albeit I was a newbie to consistent training, however nothing changed my physique such as the lower rep work. 3 months I instantly looked a lot more solid overall and pretty much base my current routine back on this very way of training.
1 - 2 lower rep 'power' exercises (3 to 5 rep range)
1 - 2 moderate rep 'hypertrophy' exercises (6 to 9 rep range)
1 - 2 higher rep 'pump' exercises (10 - 15 rep range)
Not limited to this template though. The number of exercises really depends on how many body parts I'm hitting on the day, and it is very dependent on my training split. It's more something I use for a 3 to 5 day split. At the end of the day, what really matters is the effort you put into your training. Every set and rep needs to be 100%.