There are several misconceptions out there about how writers actually work. One of them is that a person simply waits for inspiration to hit them and then goes to work creating their masterpiece. This may actually work for a lucky few, but for most writers, it doesn't come down to inspiration. It comes out of habit; one that any aspiring writer should form as soon as possible.
Developing a writing habit works for a number of reasons. The first is that it gets you set into a kind of routine that lets your brain know it's time to write. While hard to get into at first, once a rhythm is created some writers find it easier to work when they write at the same time each day. Now this time can vary for writers depending on their schedule and preference. First thing in the morning may work for some while writing into the middle of the night may be better for others. By creating a writing habit, your brain anticipates the work you are about to do. This makes the second reason much easier.
Uninterrupted writing time is another reason to create a writing habit. In order for your writing habit to be effective, you need to block off a certain period of time where you can focus solely on your project at hand. Once you pick your scheduled writing time, remind yourself that this is just for writing. Don't check your e-mail, or Facebook, or Twitter, or text your friend to find out what you'll be doing later. This is simply your writing time. If you live with family or roommates, be sure to tell them what your writing schedule is and how important it is for them to leave you to it. A writer can't get much work done if they are constantly starting and stopping every few minutes. Your writing habit should allow you to write uninterrupted throughout your whole session which will allow for a better flow of your material and a faster completion time.
By sticking to your writing habit you're also forcing yourself to write, even when you have nothing to write about. It's easy to write when inspiration hits you, but often writers get to the point where they hit a wall. Inspiration evades them, they've written themselves into a corner, or they draw a complete blank on what they want to say. This doesn't mean they stop writing. As a writer yourself, you need to learn how to push through these blocks and continue writing. Forcing yourself to write whatever comes to mind, even if it has nothing to do with the topic you're working on can have its benefits. You may not use the material you initially write, but it can always lead you to something else that you can flesh out later on. The point is to keep writing. You can always edit later.
When starting a writing habit, it can be difficult to focus, allow yourself the full time you scheduled, or stay on topic. And that's okay. Your goal in the beginning is simply to get used to writing in regular intervals. Once your body and brain become accustomed to that routine, you can start honing in your skills on a particular topic or project you've been meaning to tackle. Sometimes you may need to adjust your schedule. Life happens, and you shouldn't put off living it because of your writing. That's okay. Just be sure to make up the time later on in the day and get back on schedule the next time around.