I have tried WILD before and I just couldn’t achieve SP nor HI . But I searched the forum about WILD and recognized what SP was. 
It was described as a tingly sensation like hitting your funny bone. And I thought that I have experienced it before from meditation and I knew how to achieve it when I am trying to go to sleep. I would just have to think about something that would keep my mind focused and while doing that I shouldn’t move my body at all. And you know what, I achieved it in just some 5 minutes. 
But then I saw there was no HI present. Just blackness. So i started to think about some random scenarios and hope they would evolve into a dream, but nothing happened. Eventually my mind passed out and I started to sleep a ND.
So my question is: How should the HI come to you? Do you have to think about something, visualize that you are seeing it or they should come naturally and I just have to observe them until I am in a dream?
SP May be sometimes very mild and you do not feel anything special (no HI etc.). If you are reached awarely into sleep wihtout any visual sensation then imagination of your dreambody may help to start LD. This means that you imagine the using of your body- walking, moving hands and legs, flying or what ever. Important that you start to feel your body in dream. Visual dream usually follows to this.
Have you tried counting during WILD? Inbetween every number think “I’m dreaming.”.