Perhaps this is a little more geared towards spirituality and is actually a meditation technique, but this method has amplified my visualization capability, made my dreams more vivid, and just makes me feel really good afterwards.
The idea is to learn (memorize) the 7 chakras AND the colors associated with them, (since colors are highly symbolic) and to imagine objects which feel natural to you that represent these colors...
Start at the root chakra by visualizing the color red. Visualize this color filling up the lowest part of your closed-eye visual field. If it's dull, think candy apple red, or other items that are bright red like fresh strawberries or the inside of a watermelon. Try to make the images of these items as clear as possible in your mind's eye.
After a few moments, move up to the sacral chakra with the color orange. Again, if it's dull orange, try to imagine things which are bright orange, like a bushel of oranges... The idea is the make the colors as vibrant as possible. If you prefer to use the object as a visualization instead of merely the color, that will work also.
After that, move to the solar plexus chakra and visualize the color yellow; perhaps a bundle of bananas or a field of sunflowers.
Next is your heart chakra with the color green. I like to imagine a beautiful spring-time field of grass swaying in the wind. The more vivid the animation, the better.
Continuing on to the throat chakra with the a bright blue color, imagine perhaps a blue lotus flower, pristine Caribbean waters, or the sky on a cloudless day.
Moving up to the 3rd eye chakra is the color indigo (which is a kind of bluish purple). This one is a little harder, but I imagine looking into a black light. After a time, I started to see an indigo pine cone with the radiance of a black-light bulb. Spatially this object was about 1 foot up and 3 to 6 feet away in my closed-eye visual field.
Finally you have the crown chakra, which is either violet or white. Violet is not a common natural color, so I imagine an enormous white flower growing out of the top of my head. I try to make it clear enough that I can count the pedals.