Add volume. Higher-volume, multiple-set protocols have consistently been shown to be superior over single sets when it comes to building muscle. This is one reason why advanced lifters often follow a body-part split.
Don’t build up volume simply by doing the same thing with different implements. Change angles, rep ranges, and types of weights.
Train to failure some of the time. Yes, you can grow without lifting to the point of failure, and certain movements don’t lend themselves well to it. But all things being equal, if you stop short of failure—especially on isolation moves for small body parts like arms and calves—you won’t get the same anabolic stimulus as if you pursue those last few challenging reps.
Contain rest periods. For bodybuilding purposes, moderate rest intervals of about 60-120 seconds between sets maximize the hypertrophic response. Resting too long has been shown to be counterproductive to muscle gains because it reduces overall accumulated metabolic stress, a marker of hypertrophy. The smaller the muscle and lighter the movement, the less you need to rest.
Lift with proper technique. Don’t take this for granted! It supports everything else on this level. An exercise won’t work the way you want it to if you’re not doing it right. Get feedback on your form if necessary.