The key is relaxation. Slow your breathing and loosen your muscles. Generally, in 20 to 30 minutes you'll emerge from this exercise with a host of characters or interesting ideas for stories or poems. Before they whisk away into the ether, jot these ideas down in shorthand form or, better yet, invest in a voice-activated tape recorder and give voice to the imagery. Simply slow your breathing, relax yourself, and take in your surroundings.
Human beings are deletion creatures.
Writers cannot afford to delete information without first filtering out intriguing details which might serve as building blocks for their next writing project. Notice colors,textures, expressions, smells, and the feeling you get from simply sitting in the room you're in. Watch human behavior or subtle nuances in exchanges between other people. Finally, you must read when you can. If it's only a short while daily, then so be it.