The absolute best way to improve as a photographer is to DO photography - get out and shoot. A great way to push yourself into better photos is by concentrating on one subject over a period of time. Each time you photograph your subject, whether its a person, plant, place or thing, find a new way to photograph it. It could be from a different angle, different time of day, different light - whatever you can do to see the subject in a new way.
For this lesson, pick something near by you can photograph on a regular basis. It could be: your car, your cat, your "significant other", your guitar, what you see while walking through the neighbourhood, objects that look like numbers, rusty objects, etc.
Anything that you like to look at.
Find some object that you can easily photograph, interesting or everyday - you'll be amazed what you see with it over time.
Every day for the next 10 days take some pictures of it. Look for different ways of seeing the same subject. Place your subject in different places, different light situations, try some of the different exercises in composition - find an S curve in the subject, or place your subject into an S curve, same with diagonal lines, etc. Just keep shooting and learning about the same subject.
What you learn from this simple exercise will carry through into most things you shoot.