There are a few basic, mandatory components to muscular hypertrophy. If you want to get big(ger), you need to at least be aware of them--ideally you should be using them too. Ever wonder how the people you see at the gym can lift and lift and lift but never really get much bigger? It's not rocket science or magic--they are simply not employing proper hypertrophy principles. First we'll go into training principles, then some systemic stuff.
1. SAID Principle
The SAID principle is simple: Skeletal muscle hypertrophy is based on Specific Adaptations to Imposed Demands. It's pretty much a catch-all for everything you need to be doing in the gym. "Specific adaptations," or specificity, is a pretty rudimentary idea: It's only logical that biceps grow from biceps curls, rather than bench press, no? Once you understand that training a muscle trains that muscle; the next half of SAID tells you how to train that muscle. "Imposed demands," tells us that the muscle will not grow, or adapt, unless you signal a necessity for it. This is done through progressive overload. So you have to train each muscle individually, and you have to train each muscle hard. Eureka!
Recovery time between workouts is absolutely necessary. Not allowing the muscle to repair and rebuild will definitely lead to decreased gains; at worst it can cause injury and chronic joint inflammation. Read my post on proper training frequency here. Along with that goes the importance of a good training split.
3. Positive Nitrogen Balance
Muscular hypertrophy can be signalled via diet as well. In combination with hard training, the proper diet composition and meal spacing will tell your body how to use the nutrients you are giving it. This is especially important when it comes to protein intake. In order for your body to build muscle, a positive nitrogen balance needs to be sustained throughout the day, as often as possible. "Positive nitrogen balance" simply denotes that your body is utilizing more nitrogen (protein) than it is excreting, leading to increased saturation levels--more protein available for muscle growth and repair. So maintaining a positive balance would simple mean to eat protein continuously throughout the day.
4. Meal Spacing
Elaborating on the previous point, maintaining an even blood sugar level throughout the day is important as well. You really want as few big fluctuations as possible. This may mean adding fat to your meals to slow digestion somewhat. It may mean eating more frequently, i.e. every two hours instead of every three or four. Whatever your technique, the end result will be even nutrient flow to your body, enabling growth 24/7. For more on losing fat, read my three part series on dieting here, here, and here.