My First Visualization Exercise
Close your eyes, and imagine a circle. In this visualization exercise you can imagine it floating in front of you, or maybe think about it lying on a table, or the floor. When you have something, become aware of what you know about it - its colour, size, thickness and so on. The more things you know about it, the better your natural visualization skills. If you can that easily, move on to the next exercises.
If you only get a vague feeling of 'circle-ness' that's OK. Try developing that by imagining making the circle with your arms, or creating a circle of people. If you get a stronger response by doing that it is likely that you are one of those rare people who experience the world kinesthetically, by touch and feelings, rather that by images. That's OK too - it just means that you will end up with two good ways of experiencing the world. You should then just accept that it will take a bit longer, but you will be able to visualize eventually. Start with imagining a line, or something like a line, a rope or a stick. Then imagine the line bending. Then bend it the other way. Then get it to bend all the way round into a circle. Then change the circle into a triangle, then a square and then have fun changing to other shapes, getting them to rotate, to fold, to twist, to fill with color and so on.