It can often be a challenge to keep your mind from wandering – particularly as you get closer to falling asleep, and the hypnagogic imagery is persistently distracting you with random thoughts.
I tend to find it advantageous to lie in a position other than how I’d generally sleep. In my case, I always attempt WILD when lying on my back, because I usually find it quite difficult to sleep that way. I guess this makes it a little harder to slip unconscious before you can catch yourself drifting away. Other than that, you just need to make sure you remain firmly focused on your image (remembering to involve as many different senses as you can), and try not to pay attention to anything in the real world.
There’s a lot of information about WILD at the link below:
EDIT:
Too late. 