If you have not read our tutorials yet, I would recommend to start with that.

Induction Methods and Techniques
WILD

But even before that, if you never had a LD before, we usually recommend to start with DILD and have a few DILD, before moving on to WILD.

Sleeping postition should be comfortable, so you can fall asleep, since that is the ultimate goal. At the same time, you have to keep your mind awake and that is accomplished with mantras. If you pick an uncomfortable position, and your WILDing takes for a while, you will be very uncomfortable and it will make it hard for you to fall asleep.

Good luck and please ask if there is anything else.