Start, Then Write
You want to write, but it's impossible for you to get started. There is always a small distraction which keeps you from writing, or you spend a lot of time cleaning your desk and when you're done, you're out of time...
So, make an appointment with yourself, write it down, set a reminder and when the moment comes: you sit down and do as you're told.
Do as I'm told? Yes. You are the only person capable of getting you to do something; you just have to help yourself. Split the task of writing from the task of starting.
Find a quiet place in your house, clean it a bit and make it nice and comfy; this will be your writing spot. Place your computer, typewriter, or pen and paper on the table, and set it up just the way you like it and create a new blank draft. Think of a subject you want to write about, write it on a sticky note and paste it on your empty draft.
And now just walk away.
You have started, now you just have to write.
When your writing appointment rolls by, you sit down, read the sticky note, and you will already know what you're going to write. Your mind will have had time to think about the subject in the back of your mind, making a story and creating a first draft. Now your fingers only need to move, so your brain can export the draft to the page.
By separating the starting from the writing you will actually write something. It removes the small distractions, you need less time to fuss about your setup (because you already did) and you already know what you are going to write. It's a simple trick, but effective.
Start, then Write.