It may be easy to find a general idea for a story, poem, or even an article. But what about when you need a specific idea? Maybe it's an assignment or a themed contribution. Regardless, the idea well may dry up and you may not have all the time in the world to wait for a spark. What can you do?
Tell your subconscious what you need. I know this sounds silly, but I do this all the time and it really works. Right before you go to sleep (or some other time), outline the guidelines of your project. (For example, you need a modern mystery idea that will work as a short story.) Be specific about what you really want or need and your subconscious will deliver.
Do writing exercises with a purpose. Knowing what you want, choose exercises or prompts that seem to connect with your goal. Then write with what you need in mind. You may not get a finished product, but you will at least end up with potential concepts to work with. (Make it more fun and get a writing buddy or friend to do the prompts with you.)
Use classic brainstorming techniques. You probably have your favorites. I always lean towards clustering or listing. If you're really stuck, try a technique new to you. Getting out of your comfort zone may unlock of host of potential beginnings.
Relax. It's easy to stress when the ideas won't flow, but that's the worst thing you can do. So do your best to chill out so you can focus on your writing and not on the fact that you don't have any ideas. Listen to music, take a walk, work on another project for a while - whatever helps you to relax so you can think straight and be productive.
Using one of these methods or a combination will help kick start your creativity, but in a more focused way. Instead of shooting out random ideas, you will get specific ideas so you can move ahead with your project.