This question greatly occupied me in my younger years. Where do original ideas come from? What can one do to make them come? Something I have discovered with age is actually that this problem is generally not one worth worrying about.
In fact it is not difficult to have original ideas. The main thing that creativity requires is time: you need to be prepared to set aside time to explore whatever it is that you are trying to create, whether it is a piece of art, music or literature. It is no good trying to force things, but, from personal experience, I normally do find that if I decide to make the time to work on my music, something will come. What is required is a willingness to explore one’s own ideas, to see where they are going without being excessively self-critical.
There are some things that are the enemies of creativity. Firstly tiredness, it is no good trying to do anything when you are simply exhausted, much better just to get some sleep. Anything that befuddles the senses, such as strong liquor and illicit substances, is a killer of creativity. I know that there are people who fondly believe otherwise, but I think that this is because creative people sometimes have a strong personal attraction to drink or drugs. But if they manage to create original work it is usually in spite of the substance use, not because of it.
The other enemy of creativity that I touched on above is excessive self-criticism. We all need that inner censor, who tells us when an idea is rubbish, and not worth pursuing. But the censor should not be allowed to wield excessive power, we should not allow it to cut off ideas before they can be explored. When I try to compose music I don’t know ahead of time whether what I write will be good or not, in fact one of the joys of composition is the constant surprise at what comes out.
Sometimes when I make a start on a piece I have a good idea of what I am trying to achieve, for example the Partita for Solo Flute is something that I had in mind to try and write for some years before I actually got around to it. I had a fairly clear idea of what I was trying to achieve before I started. However just as often I really don’t know what I am going to produce, it just happens. Of course it doesn’t really, I guess that the ideas are being mulled over somewhere in my unconscious mind. The important thing is to get into the habit of writing regularly, to make oneself product something, good or bad. The more it becomes a habit, seemingly the easier it becomes to tap into that unconscious source of creativity.
So make time: practice your art. It is not difficult. There are other things that harder in my opinion, like how to find your own authentic voice, which I may write about some other time. Sorry if you were expexting something more profound, but I think that the big secret is that there is no secret.
Meanwhile the last word from someone who really did know about being creative: