A common problem for many guitarists is what I call the intermediate plateau. As a beginner, you improved rapidly. You got faster and more fluid almost on a daily basis. Then it stopped. However hard you practice, you don't seem to get any better.
The solution is simple and often unexpected. To get better you are going to have to retrain your fingers and approach things in a slightly different way. It all comes down to pressure. The amount that you press down on the strings to make a note.
When you start learning the guitar, your fingertips are soft and your finger muscles are weak. It takes a lot of effort to hold down the string to make a sound. This is often made worse because (like me) people often learn on cheap or old guitars with a high action. As we get better at the guitar, our fingers get stronger and the tips tougher. We don't need to press so hard, but we still do because it has become a habit. By pressing too hard, we are wasting energy and increasing the muscle tension of our fingers. Both of these things combine to slow us down and stop us playing smoothly. So, all we have to do is learn to press more gently.
We are going to have to go back to the beginning and retrain our fingers on how to press down on the string. It will feel like being a beginner again, but I promise, if you follow the exercises correctly you will improve dramatically in a short space of time.
To start, we will need to know how hard we need to press. So, hold down any note you like with your first finger. Now repeatedly pick or pluck the note while gradually releasing pressure on the string. There will come a point where the note becomes muted, buzzes or stops completely. Now put on just enough pressure to make the note clear again. This is all the pressure you need. You should notice how much less pressure you are using compared to normal. Next, we have to train our fingers to only play with this pressure and no more.
The exercise we are going to use may be familiar to you. It is a simple exercise that is often given to beginners, but we will have different goals in mind. You can start this on any fret you like, and it is worth practicing at a different point of the neck, but we are going to start at the fifth fret. Your first finger is going to play the fifth fret on the low E string, then your second finger will play the sixth fret, your third the seventh and your little finger the eight fret. Then repeat this on the string below and so on until you run out of strings. Then play the whole thing backwards until you get back to where you started.
Always when playing this exercise, it is important to make sure you use alternate picking (up, down, up, down), keep a steady rhythm and produce clear notes. We want relaxed accuracy, not speed. To make us press lightly, we're going to use a little trick. It is very difficult for our two hands to do two totally different things. So to make our fretting hand press lightly we need to make our strumming hand play gently, too. The best way to do this is to practice the exercise while trying to play as quietly as possible. You still need to be playing clear notes, but someone sitting next to you should have to strain to hear you.
Play the exercise a few times slowly and quietly. Focus on the fretting hand and pay attention to how it feels. Remember how light you press and make sure your hand stays relaxed. Next, try picking harder and louder while maintaining the light pressure of the fretting hand. This takes a bit of getting used to and should be practiced every day (or every time you play). One or two minutes a day is all that is required to make all the difference. After the first week you should already notice a difference.
Once you start to get comfortable playing the exercise gently try playing a tune or riff that you are familiar with. Pay attention to your fretting hand all the way through and keep it relaxed and pressing lightly.
The last bit of advice I can offer on getting better is — don't try too hard. The more you try to play faster the more tense your muscles become and the less able you are to play fast. Instead, start very slowly and practice so that things sound good and feel easy to play. This will mean that you are learning good technique and the speed will come naturally after that.