John Scalzi, in his "Whatever" blog, encourages would-be writers (and those of us who have fallen off the wagon) to stop answering "Do you want to be a writer?" with "Yes, but..."
So: Do you want to write or don’t you? If your answer is “yes, but,” then here’s a small editing tip: what you’re doing is using six letters and two words to say “no.” And that’s fine. Just don’t kid yourself as to what “yes, but” means.If you really, actually want to write, he says, you'll do what it takes to find or make the time and space to see that you do it. Scalzi advises those who would write to dedicate themselves to a set number of words each day. He suggests 250, but that feels low for me... I'd aim at at least 500 for myself.
John Cleese advises the two most important things for a writer to stake out for him- or herself are space and time. Find a place where you won't be interrupted and set aside a finite span of time in which you will write. Fifteen minutes, half an hour, an hour, whatever you can spare or feel comfortable with. There's a video of him talking about it on the I Should Be Writing site.