I admit that I have dabbled in the practice.
It was a long time ago and I probably didn't do it properly.
Pretty sure it opened me up to a different level of attack - for a very very long time.
I personally consider the practice to be 'potentially dangerous but absolutely obtainable'. Proceed with caution.
For those who still wish to proceed...
Practice your lucid dreaming (catching yourself dreaming - and actively changing the reality within your dream)
Face up - in bed - comfortable temperature. Loose comfortable clothing.
Ease your breathing. Relax. Feel rather than think (or think very simple thoughts).
As you feel yourself drifting into sleep, picture yourself shifting downwards into your bed - as if you are going under - without twitching a muscle.
Then, reverse. And repeat. A few cycles and complete relaxation in near-sleep should do it.
Hint: If you start above the covers - and after you are done, get under the covers - you'll be one step closer to knowing if it was a dream or not.
Good luck.