Don't concern yourself with SP, just focus on falling asleep consciously. I always just sleep in the most comfortable position and move whenever I need to. The problem with many of these "OBE" teachers is that they teach you to stay awake; therefore you can spend years entering vibrations and other sensations without ever being able to "exit". You must fall asleep, and focusing on SP is in my opinion a great way to prevent that from happening. Take a look at some of the WILD tutorials here to get a better idea, and good luck.