use a book from your bag or go to webster.com. Open it up to any page and pick a word or use the webster word of the day. Don't like it? Pick another. Not ready to be completely aimless? Find a page and word that draws you in.
Don't use the process repeatedly to find a word you already have in mind or one that fits your mode of thinking. Let randomness take you in a direction you wouldn't normally go. Using this word as inspiration let your words flow onto the page about what this word means to you. what this word makes you think of. If you don't know the definition make one up.