Everything comes from something. Your writing comes from your entire life: everything you've done, witnessed, and experienced. And everything you've read. Unfortunately, when you sit down to write, you may feel as if your mind is a blank slate. The cure? Notebooks.
Get into the notebook habit. You can keep your notebooks on your computer, in paper notebooks, or on index cards, your choice.
The benefit of writing notebooks isn’t in the notebooks themselves. It's in the writing you do in those notebooks. When you write something down, you'll remember it, and it will come out in your writing sooner or later. No more blank slate. :-)
Start a Conversations/ Dialogue notebook.
Write at least one conversation you overhear today, either at work, in a restaurant, or in some other public place. Describe the people having the conversation. What does each person want from the other?
Dialogue tip: dialogue isn’t just conversation.
When you're writing dialogue, beware of writing small talk. In a novel, short story or nonfiction, your dialogue must have a point. It's not greetings, and it's not small talk. Watch a TV show like "Law and Order" to get a feel for the way dialogue conveys information, and characterizes.