It is said that you cannot improve anything if you cannot measure it first. Creativity is no different. You need to be able to measure your creativity before you do something, and after you do it, to see how much you improved, if at all.
There are many ways to improve creativity, from avoiding certain frontal-cortex-stimulating activities to participating in dangerous sports, and even to zapping your brain with alpha waves. There are also courses that you can take. But how do you know if doing any of these things has made a difference?
First, we need to accept that creativity covers multiple areas, from drawing to story-telling to inventions, and it can be written or verbal, so it is hard to find one set of parameters that can measure all of these areas.
However, a set of four dimensions was developed and is measured by the Torrance Test of Creative Thinking (TTCT). It takes approximately 30 minutes to measure, and will provide you with four scores on those dimensions. There is even a Silicon Valley startup that will measure your creativity based on the TTCT framework in 20 minutes, for $35, completely online from the convenience of your computer.
Below are the four parameters (sometimes collectively referred to as FFOE). To illustrate them better, I have included an activity that will allow you to measure, albeit subjectively, the creativity of individuals, and compare them to one another. These activities can also be done in teams, allowing you to rank team creativity.
In front of you is a pen (or a paper clip). In five minutes, write down every single idea you have for what you can do with that pen (or paper clip).
The measures the sheer number of ideas you have. When you are being asked to provide ideas, how many ideas do you have? In the activity, the more ideas you have, the higher you rank on fluency. It is important to note that the usefulness of the ideas, the feasibility of them, and how much they differ from one to another should not be judged at this point. Only the number of different ideas should be counted.
How different are the ideas from one another, and how flexible are you in how you use them? Using a paper-clip to join paper together ranks very low on flexibility, because this is the natural use of paper clips. Using the metal in them to create ball bearings is a more flexible use. If the individual (or team) presents multiple ideas, but ones that are very close to one another, they will still rank relatively low on the flexibility scale.
How different are the ideas from the original use of the paper clip or pen? "Writing with it" would rank very low on originality. Breaking it apart into its different elements and suggesting uses for these parts that are far from what the pen was designed for would rank high on originality. Describing uses that are achieved today with other products that look relatively similar would rank in the middle.
This is about the amount of detail that you provide with your descriptions. A very brief description that lacks detail and fails to explain how can you turn the product in your hand into the product (or use) you are proposing will rank low. However, providing a great amount of detail will go a long way toward proving implementation feasibility, and rank high on elaboration.
Besides simply allowing you to assess the quality of your ideas, this can also be a useful exercise if you're thinking about patenting a product or process you've developed. When filing a patent, there are three tests for the validity of that patent: novelty, usefulness, and feasibility. Creative ideas that rank high on flexibility and originality will meet the novelty requirement. Ideas that rank high on elaboration would go a long way toward meeting the feasibility requirement.