I’m having a hard time noticing HI. It’s probably because I don’t really have a full understanding of what it should look like. I know people say that it looks like hypnotic patters…But I don’t really ever notice that while I’m relaxed. When I attempt to WILD or some other technique I relax and I try to not let my mind wander. But then I guess my mind subconsciously thinks of these dream-like situations as I drift off, but I’ve never experienced any sort of SP or SP ever for that matter. Then when I realize that my mind is drifting I start to concentrate again. I guess I need a clear and full understanding of what HI is, how I can notice it, and how I won’t drift off to sleep.
Well, HI can be anything from patterns of colors to full detailed images. I guess it’s hard to understand if you haven’t had any. As your trying to WILD (specially if you’re close to falling asleep, I think) try to look into the “darkness”. Try to search for any difference in the black that might be part of an image. I’ve had full detailed HI come out of nowhere, but I think usually you start with gentle impressions of images. That is, you kind of might not see anything at first, just have an “idea” of a house, for example. Then it should start getting more detail.
I’m not sure if I explained it that well… 
Some people MIGHT not see any hipnagogic imagery at all. While I do know what it is and seen it very breifly, I’ve never really seen a full fledged one. The most basic one can be done while awake without even trying to WILD. Just close your eyes and and you’ll most surely see something other than darkness, most surely very faint. When I do so I see something that looks somewhat like color worms or bacteries moving around my field of vision. Give it a try, or use another method for WILDing, such as breathing.