The Well of Creativity by Reginald Thomas Jr.

Many people have a problem being creative on-demand. There's a saying that goes, "A professional is someone who does his best work EVEN when he doesn't feel like it." Fortunately, for me, I am in a business where I constantly have to produce on demand. This has trained me to learn how to be creative in a stressful environment.

Originating Ideas
My first attempt to cure a creative block or even if I need some inspiration when working on a new project is browsing through my library of reference books. These are usually in the form of some art books or magazines. The intent is to stimulate the creative juices, not to steal ideas, but to look at another person's approach to a design problem and possibly gain insight. Looking at good design usually inspires me to start creating something of my own.

Utilizing "Happy Mistakes"
A random event that can turn into a great virtue that can aid you immensely in your creativity is what is called the "Happy Mistake." Happy Mistakes are usually errors committed in the early design phase that can change the way you look at the original intention of the design, even changing your design entirely!

Iterations, Iterations, Iterations
Finally comes the subject of iterations. Some of the artists I've known in the past have the thought that the first idea that comes to them is good enough to be their final idea. They believe they can't improve on their first design. While this may, just MAY be true (more likely if they are their own client), in all probability the first design could just be a good start to several great designs. Iterations are the act of repeating a design with different variations to achieve the final goal of a design or purpose visual, mechanically or organically.
Personally, with a new design, I try to do four to ten different variations of a design to nail the concept in place. If it's for a client, I might even do more than that (depending on the deadline). When you have the iterations all done, it's easy to look at them and decide what works and what doesn't.

In the final analysis, it's all about using the fire of other's people's design and artistic expressions to re-kindling the fire of your own creativity and keeping an open mind to capitalizing on your own mistakes.