First thing I would suggest is that you need to have reasonable expectations. For example how much muscle mass can you expect to gain? Based on a study if you train properly, you can expect to put on 20-25 pounds of muscle mass. But once your body gets used to the training, you will experience progress slower and less than when you first started out. Based on the same study in your second year you can gain 10-12 pounds and 5-6 pounds in your second year.

Next one is obvious, you need to keep your diet in check. Keep a track of your macros, and shoot for a balanced diet with fats, proteins, and carbs. Very basic estimation of protein intake is to consume 1 gram of protein for 1 pound of body weight. It is not necessarily useful to take in extra protein as your body cannot absorb it and will flush it out.
Another important thing would be to utilize micro nutrients in your diet. Most people do not pay attention to this. Everything from rest, training, and hormones are affected by micro nutrients. There are many vitamins and minerals that are great for performance. I suggest taking a good multi vitamin or eating veggies every day. Another important thing is to split your meals. This ensures a steady supply of nutrients to your body. This is very useful when it comes to the protein intake. Your body can only absorb a certain amount of protein at a time. If you space out your meals and protein intake this will be a more efficient way of consuming protein.
Next would be to lift heavy. I have talked about this before as well. To ensure muscle building when it comes to lifting is to make sure your body doesn’t get used to your workouts and the best way to do that is to increase weight on your lifts often. Ideally this would be to increase weight each week but that is not very ideal so it’s important to attempt PRs each month or once every two months in my opinion.
There are other method to ensure that your body does not get used to your workouts. For example drop sets, burnout set, and super sets are a good way to change things up. Another thing you can do is to increase volume. Have a week where you increase the volume on all your lifts. Lastly I would say is that compound lifts are vital to muscle growth. Compound lift do not target a specific muscle but they workout many muscles and these are the lift you can go really heavy on. They activate core, lower body, and upper body. And they also help release human growth hormone which is directly related to muscle growth.
To end… One thing I like to think in terms of fitness is that you will get out what you put in. Fitness is all about being honest with yourself, being honest about the work that you are putting in. There are many things in life that you have no control over. For example no matter how much effort you put in a relationship or at work or basically anything else… there are no guaranteed results. However with fitness that is not the case. You get out what you put in.