Now scheduling writing time comes from what I was doing a few years ago when I was pursuing a doctorate, having a full-time professional writing job, teaching two courses, and trying to have a semblance of a home life all while occasionally sneaking in some creative writing. My schedule sounds impossible and there were a few compromises (surprisingly few) but I successfully worked full-time, received the doctorate (with a GPA to become a member of the Delta Mu Delta honor society) and taught two classes worth of students per semester. I'm telling you this not to brag, but to say "I did it and so can you!" The key to it is, don't think about it, just schedule it & do it.
First schedule time, even if it is only 30 minutes a day. Try to schedule multiple times per week to creatively write if you are seriously wanting to be a writer. That philosophy is good for other types of writing too - I do technical writing as well and that's how I learned to do it, by practice. Don't expect that you will be an overnight sensation. I believe in a thing called the 10,000 hour rule. This means that to be an expert (or at least very proficient) you need 10,000 hours of doing something. I once did a calculation and it reminded me of my doctorate which took 5 years and at least 30 hours a week (sometimes more on holidays and vacations).
Pretty much in the end, 10,000 hours. Remember you are in it for the long haul, so schedule time. If you carve out time for the gym each week (say 4x a week for 1 hour each) you can schedule your writing time too. You won't have the crazy schedule I did and so you won't have to tightly schedule everything. I used every bit of time I had. Sometimes lunch was the only time I got 15 mins. of creative writing in during the week or waiting for an oil change at the dealer. Needless to say, I rarely watched TV during this period and was really reminded how much time is lost to bad viewing habits.
Second have material you want to work on. Not what you feel others want to see. My first fiction book didn't excite the agents I sent it to. I'm fine with that, realizing my writing has improved by experience and feedback and am in the process of sending out other books I have written (they are a different genre). Working in the entertainment industry for many years I have come to realize there isn't a sure formula for success, never-the-less I came up with one. I've never known anyone in entertainment to just fall into success by just getting a big break with no work. So called "breaks" are merely an equation (yes which I love since I am a former engineer & system admin.).
Big Break =
Enough Time Spent Doing + Good Luck + Love of What You Are Doing
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Tenacity + Love of the Craft
Both "loves" feeds the "tenacity" though not perfectly represented, is really important in my opinion. Finally believe in yourself and your vision. Once you are in the schedule of it you'll find the time flies and you want to schedule more. Having multiple ideas and projects assures you have something to work on. That has been my journey.
