Some people think composing is this miraculous thing that only genius's do. What a myth! It's a skill that can be learned. What can't be learned is the intuition that guides the creative force. What can be learned is the technique. And the most important part of composing technique has to do with THINKING IN PHRASES.
A musical phrase can be 2-bars long. It can be from 4 to 8-bars long as well. It is a unit of music that composers use, along with repetition and contrast to create ENTIRE SECTIONS OF MUSIC. There is no secret here people. It's like building up a structure. That's why music is often referred to as frozen architecture. It is built up. The building up creates FORM. A structure such as ABA form can be composed of the A section (8-measures) B section (4 or more measures) then back to the A section.
Now you may be thinking, it looks logical but how does it transfer into actual music? Ah, this is where you get your feet wet and actually try composing a piece. We start from simple means and learn the principles of repetition and contrast first. We start with an 8-bar phrase for the A section.
Now a problem arises. How do I fill up this section? You can either start with the melody or with the chords. If you've had a chance to look at my free lesson, you'll see that by improvising, MATERIAL IS INSTANTLY CREATED! This solves your problem doesn't it? Now, you may be thinking, how do I get this material into the 8-bar framework you've been talking about? First, you need to be able to count in 3/4 or 4/4 time. Not very difficult but if you can't do this now, there are many sites on the web that can teach you this.
Now it's just a matter of transferring this raw improvisational material into the 8-bars. Most likely, you will be jotting down your chord changes. I explain this in a lot more detail in my online class. It's a quick sketch method. You have the raw uncensored germ coming from your improvisations - you then write down what chords you are playing and perhaps the first 2-bars of melody so you remember what the initial impulse was.
The reason I use the 8-bar phrase is that it is a nice unit of time to work with. I don't try and reinvent the wheel here. It's been used for centuries and can be used in New Age music as well. Once you have this 8-bar phrase you can repeat it and add in another section (B) to add contrast.
This may be hard to understand by just reading about it. You have to do it in order to really understand.