For me it is WILD the best way but it took me almost a year to get it at that level. The biggest mistake one can do is just lying in bed and waiting for a dream. Doing that you’ll get to a point where you gonna end more awake then you were before bed and it could cause insomnia… [I’ve experienced that]
I like to divide WILD into 3 steps:
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WBTB - you need to find good time for WBTB, of course you need to experiment with that… Usually waking up naturally is the best way because it’s going to be natural and calm waking… Also you need to find out for how long you need to be awake to awake your mind but keep your body asleep. Even 5 minutes may be enough.
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SP - also a lot of experimenting… the biggest mistake I was talking about is thinking that you can just end up in a dream, well you can’t you need to fall asleep eventually. So the SP is only a bridge to a dream world but you need to know when you should let yourself to fall asleep - which is step 3:
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Falling asleep: this is the crucial step. After experimenting with SP to see how long you experience one and how you feel at different stages of SP you can determine when to fall asleep. The point is falling asleep easily and when you feel like you can’t struggle any more then you let yourself to fall asleep and you may at that time experience vibrations, very odd combination of sensations[although that’s how it looks for me but you may experience something totally different, that’s why you need give a time to tech a do some experiments!]. And that part with falling asleep needs to be conscious. That’s mean that you need to think something like this: Ok, this is it, that’s the part about which that dude talked on LD4all and I will now let myself to fall asleep! After that I say that transition from waking world into dream world last’s only a few seconds, maybe it doesn’t but doesn’t matter because you will most probably be lucid from the start.
I’ve learned that nothing is almost instant and by accepting that you will have better and quicker results!
It depends on how tired you are and how comfortable you feel in the position you are trying to fall asleep!
I don’t know that in time because I’ve never end SP intentionally just to see how much time passed.
Yes it’s possible but have on mind that if you get to some point in SP and if you drift off[which practically you need to do but at the right moment] you will still end in a dream with some awareness and you may have lucid dream or better recall or more vivid and life like dream…
I hope this helps, if you have any more questions just ask! 
EDIT:
Also if my post is not easy to understand read main post in this topic, it may provide some better answers but basically I said the same!