I'm no teacher, but I did find a pretty neat way to at least get you to start. Ironically, it was from CA.org >_>...
http://conceptart.org/forums/showthread.php?t=81332If you are too lazy to click on that link, I will copy/paste the most essential things so you can get to work.
These assignments should help you to answer those questions.
*********Assignment #1: From Still-Life to Imagination************
Pick a real-life object to draw. It can be a shoe, a car, a tree – anything that is available to you for direct observation. Take your sketchbook to it and draw it. Leave space on the same page or a facing page for the second part of the assignment.
Using that first drawing as a guide, draw the same object from the same position – but change it somehow. Add an imagined element. If it’s a car, you could change the curves of the lines to make it look like it belongs in a science-fiction movie. Or turn it into a hovercraft. Or give it a crazy flame paint job and fins and monster truck wheels. Or make it steam-punk, or aquatic, or turn it into a thousand-year-old rusted wreck.
By doing this in two steps, you have both the benefit of direct observation, and you get the challenge of coming up with something from imagination and communicating that thing.
********Assignment #2: From Self Portrait to Imagination************
Self portraits are hard! They are also the best way to prepare yourself for drawing one of the most difficult and yet ubiquitous subjects that every illustrator must draw: the human. If you want to be an illustrator of any stripe, then you must learn to draw people. Don’t be afraid of messing up; just try it and keep trying it until your results don’t stink.
For this assignment, set up a mirror and draw yourself. No, don't use a photograph, use a mirror. All drawn? Great! Now add some invented element to your drawing. It could be a crazy hat, or a plate-mail shirt, or a crazy facial tattoo. You can turn yourself into a Klingon, or add faerie wings.
Whatever you add, the challenge will be to make the imagined elements look like they belong in the drawing. It should look like the entire image was drawn from observation.
*********Assignment #3: Half-Imagined Environment***********
This assignment is just like the Self Portrait assignment, except instead of drawing yourself, draw a landscape or interior space. Add in an element from imagination. For instance, you could draw a hallway in your home, but draw in a giant crack across the floor filled with lava. Or draw the buildings along your street, but give them turrets and towers and cannons. Or draw a field with trees, and add a herd of invented animals.
Once again, the challenge will be to make the imagined elements look like they were observed along with the observed elements.