The only time I fall asleep in less than 5 minutes is if I am completely exhausted. I have to go through a mental winding down period while I lay in bed. Usually through reading or just closing my eyes and thinking about something pleasant. This usually takes me about a half-hour on average. Anyway, from my point of view, I never understand how someone can just lay down and be asleep in a few minutes.
It's called sleep envy and, some nights when I can hear my wife drift off in minutes and I'm not even close to it, it throws me into that mental tailspin that goes through multiple stages like the whiny "why-me", plain anger, frustration and more. The only result, of course, is an even more delayed start of sleep phase.
I count numbers from 1 to X, where X is the number I get to before I fall asleep. I concentrate on the numbers and nothing else. Eventually I get to X and I fall asleep. The speed of counting should fast enough I am not bored, but not so fast that I have to spend effort. The speed varies depending on how close I'm to sleep. The closer I am to sleep the slower I count.
I do the same but I also visualize each number differently; different shapes, textures, sizes. That seems to help engage the monkey chatter and the wacky visualizing takes me closer to dreamland.
Plus one for F.lux, I have it on everything I use but recently I updated my phone to the standard IOS thinking it wouldn't be missed since it was the only Jailbreak tweak on my phone, but now I'm missing it so hard I'm seriously considering an Android and its equivalent app. With F.lux on my phone my light sensitivity was better in the day and sleep was better at night.
It's exactly like counting sheep, except counting sheep doesn't work for me. Either every sheep is the same, I get bored and revert to background chatter, or every unique sheep takes too much effort to imagine, I revert to background chatter.
Perhaps they read in bed, or otherwise have a calming period (yoga, meditation, etc), before they consider themselves as lying down to sleep. e.g., they lie down in bed, read for $(time), and then put the book away, turn out the lights, and lie down and fall asleep.
