Building muscle is no easy feat. But the majority of information out on the internet makes it seem like you can look like Hercules in 6 weeks.
I am forever grateful for some of my mentors growing up. They instilled patience, discipline, and told me to always be a student rather than a guru when it comes to exercise and building muscle.
The best piece of information I ever received was to seek perfection in your habits and in your movement skills. As your habits and skills improve, so will your results.
2 Keys to Increasing Lean Muscle
Quality
Mechanical tension is important and will forever be an important factor in building muscle. Putting more weight on the bar and increasing personal records on 5-10 rep maxes is essential to increase muscle size. Quality can refer to a number of things. When you are in the middle of a challenging set you tend to lose some common technical proficiency's. Your tempo increases, your body is less stable, and you use too much body English. Having a 315lb bench press is awesome but if your butt comes off the bench 6 inches then is it really doing you a lot of good?
A set of 20 pull-ups with a half range of motion is good. A set of 10 strict pull ups with a full range of motion is great.
A set of bicep curls that resemble a clean and press may make you feel a pump. A set of strict bicep curls with shoulder blades retracted and elbows at your sides will provide a greater stimulus.
Stress
Stress is normally a negative when it is used in real world context. Training stress is simply the work/rest ratio of your training sessions. Metabolic stress is the burn sensation that comes when you do a grueling set that makes you cringe at the end. It is an important parameter in training but totally ignored by most lifters.
The main goal should always to get a little stronger over time. But another component is to perform a max amount of work in a short period of time. Gains are made when strength meets metabolic stress in a controlled and safe fashion. It is ignored by most lifters and not put in programs because it is uncomfortable and pushes you to your limit. But this is a challenge that you should welcome and also try to progress in. It will be to your benefit to include sets of 10-50 reps sometimes in your training program. Aside from the muscle building benefit, they help you create a form of grit and determination that will enrich all areas of your life.
For anyone interested in getting bigger, or stronger the concept of progressive overload must be embraced. The simple act of adding weight to the bar each workout is a valid approach whenever you can pull it off. As a beginner, it works well but those days will fade and quite frankly you want them to happen sparingly for safety reasons.
You should be open to all the possibilities to gain muscle.