I would suggest not to compromise with your sleeping hours. Sleeping prepares the body to recover from the wear and tear of the body occurred due to routine day workout. The more deep sleep, the more refreshes the body.
In view of the above, if you still intends to shorten the sleep, you would have to practice yog nidra. For this successful achievement of yog nidra, you will have to practice many things - body purification (through yogic kriyas that cause mental and physical purification - niyama, yama/kunjal, neti, bhastrika, shankh prakshalan, etc. - these will speed up the success of effects of yog nidra), sattvic diet (simple vegetarian diet) and meditation exercises.
Steps of yog nidra are as follows:
(i) Body relaxation - Lie down on your back on plain surface. Close your eyes. Ensure that you are not disturbed by the outer noise or some agent like cold of the winter (in that case, you may cover your body with some warm cloth). Step by step first relax your body by sensing each part of the body as relaxing. Start with toe of the left foot and slowly raise sensation toward upper side of your body covering each part of the body till you get to the top of the head and slowly down toward toe of the right foot covering each part of your body. Sense back of your body - sense those parts which are touching to the ground. Repeat for a 2-3 cycles.
Breath Relaxation: Now come to the breath. Sense how the incoming and outgoing breath is touching walls of your nostrils. Observe for a few moments. Then, sense the breath, without any interference with the breath. Do for five minutes.
Mind Relaxation; Think that your all thoughts are falling down. Repeat for few minutes. Now, think that this thought that all thoughts are falling down, is also falling down.
I would not suggest the above practice to do without any qualified instructor. Better to approach the instructor and discuss with him and he will guide as per constitution of your body and purpose of the yog nidra.
