A trick I often do to get myself to sleep when I'm wide awake is to have a scenario in mind that I think through, like a film if you like, and this works every time. The scenario changed over the years, but it's an unfailing trick I use to drop off to sleep. Not a dream really, but kindof related.
This was a cross between Aliens and Terminator. I was a freedom fighter against Aliens/Robots that have taken over the world. The landscape has been bombed and derelicted (sp?) and I lead a team of friends (all recognisable people from my life) who've had to take up arms and become soldiers to fight off these baddies. I am not the top leader but one of the important general types. We have to go into places (my old school, shopping centre, etc) and blast away at anything hostile, and pick up survivors (who will also be people I know). I inevitably rescue the girl I used to fancy at school, and she falls in love with me. We fight side by side, although she always has a tendency to get injured. We have to explore disused Alien/Robot bases, and get to pick up lots of cool gadgets ands weapons.
I am living a live action version of the old BBC Micro game Elite. I am not the pilot of a Cobra MkIII but the weapons and technical guy. I patch up the ship, and do all the computer stuff. My collegue (someone I know) is a gung ho pilot but I am the dependable one. There's a pretty girl in admin on one of the space stations that fancies me.
I have a boat tethered in the harbour, a big sailboat that you can live on. My youngest son and I take a dinghy out to it in terrible weather, almost capsizing, before making it onto the deck. We struggle into the body of the boat and shut the door. Inside it's warm and comfortable, and though we can hear the storm rage and feel the pitch of the boat, we're safe and secure and I can make us dinner in this cosy little place, before settling down to watch TV/read/sleep.
This latest scenario usually has me asleep before I've even got onto the deck.