I have tried WILD a few times in the past, and last time was a few days ago.
As far as I know I don’t get any HH or anything like that, the closest I have been to hallucinations was that time when I woke up in the night and then saw vague geometric figures behind my eyelids when I went back to sleep - but I’m not sure I remember that right, but I think I saw things like that.
Anyway - which signs should I look out for if I don’t get any hallucinations of any kind?
On my last attempt my left elbow suddenly twitched and then I felt warmer and more distant from the waking world, but I was still aware that I lied in bed and I could also move my body even after a pretty long time - and then I fell asleep and got a normal dream.
Did I miss my chance to turn it into a lucid dream or how are you supposed to do if you don’t get dream magery etc?
Because it feels like I’m lying there forever just wondering when exactly the dream might start.
Okay. No.
You must absolutely not wonder or ask yourself questions, or even wait for anything !
you must literally fall asleep ! How will you fall asleep if your questioning yourself ?
Simple, i too don’t have HH, or nearly !
When you WILD, trust me, you will now it. You WILL feel vibrations before the SP, and trust me, if you do what i said above, that will come.
Nevertheless you need practice to fall asleep while keeping yourself aware of it.
To answer, you might fell lightheaded, and like you said, you feel yourself drifting away. You may also feel numb.
And no, you don’t need to see images, when you are in SP, just imagine what you would see behind your eyes 
Follow my tips
Hoping i helpt ! 
Samyten
SP is the signal you’re doing it right. When it comes, you should have your eyes closed and imagine entering a dream. I have no HI for all intents and purposes, but I can still WILD.
Also, don’t try WILD as soon as you go to bed, I read everywhere it won’t work. Try it after you wake up at night, you should go to REM faster that way.