Here is an excerpt from my book, The Silent Master: Awakening the Power Within:
Concentration requires quietude, perseverance, and self control. It is a process which can be carried out in formal meditation, and also a process that you carry out every day in all kinds of little ways. (This is covered in Chapter Six.)
Concentration is a discipline. As you discipline your mind through concentration, your mind becomes like a student. You help your mind learn to focus only on what you desire to create, not to bubble and cook in a stew of unwanted self destructive thoughts.