Shift,
Here is the technique I use.
Begin by sitting in a full or half lotus, or in a high backed chair with your feet flat on the ground, even flat on your back is ok, whatever position is comfortable as long as you keep your back straight.
Place your hands palms up on your thighs (lotus or chair) or by your sides (if on back) with the thumb and index finger touching lightly to form a loose circle.
Breathe deeply and slowly, in through the nose out through the mouth.
Close your eyes.
See the color red in your minds eye, vividly. If you have trouble, envision an apple.
Then
See the color orange in your minds eye, vividly. If you have trouble, envision a orange.
Then
See the color yellow in your minds eye, vividly. If you have trouble, envision a banana.
Then
See the color green in your minds eye, vividly. If you have trouble, envision a green plant.
Then
See the color blue in your minds eye, vividly. If you have trouble, envision the sky.
Then
See the color purple in your minds eye, vividly. If you have trouble, envision a plum.
Do not worry about indigo.
Remember to go slowly, and see each color clearly.
At this point you will be in a deep meditative state, allow your thoughts to gently rise, but do not hold onto or dwell upon them.
Gently begin to follow your stream of thoughts down, down, down to where they originate, do not be frightened by the roaring in your ears or the shaking of your body, this will soon cease.
You will find the place you arrive at very interesting, trust me.