For the beginning guitarist most of your practice time is not going to sound very musical. Before reaching the point of being able to freely express your musically the muscles in your hands need to be conditioned. Strumming patterns, picking techniques, and chord positions need to be committed to what is commonly referred to as muscle memory. What that means is going through the same motions hundreds and perhaps thousands of times much like a martial artist repeats the same movements over and over again.
Just as athletes need to endure hours and hours of exercise and physical conditioning before stepping onto the field or into the ring, it will be necessary for you to invest many hours working on the coordination and strength of your hands. Over time you will be able to begin to express yourself in the way you desire.
Here is a very simple but effective exercise that will build the coordination of both hands and improve your picking speed and accuracy. Throughout the exercise you will be alternating between down strokes and up strokes on one string at a time.
Begin with the pointer finger at the first fret of the low E string (that's the thickest string). Using a down stroke pick that note. After picking the first note the middle finger now goes to the second fret of the same string. Pluck this note using an upstroke. Immediately place your ring finger on the next fret plucking it with a down stroke. Place your pinky finger on the next fret and pick it with an upstroke.
After playing these four notes on the low E string using alternate picking you will do the same pattern on the A string which is the second thickest string. After the A string move to the D string and so on until you have played the notes in the first four frets of all six strings.
Next you will play the same thing in reverse beginning with your pinky at the fourth fret on the high E string (the thinnest string). Strike this note with an upstroke followed by a down stroke on the third fret an upstroke on the second and another down stroke on the first. After playing these four notes move to the next string repeating the same pattern until you arrive once more at the first fret on the law E string.
As you do this exercise you will immediately notice that it does not sound very musical. Pushups, pullups, squats, and the benchpress don't look like football either, but those exercises are vital in preparing the athlete to play the game. In the same way simple exercises like the one just described are also vital for you to be able to effectively play your instrument.
Once you are comfortable doing this exercise beginning with the pointer finger on the first fret move on to the second. Play through this same pattern of up and down picking with each finger being covering one fret on each string at a time as you move up and down the neck of the guitar. As you exercise concentrate on keeping consistent timing. Play as slowly as you need to in order to play the notes cleanly. Over time your speed will increase as you work this exercise into your daily practice routine.