I suggest (as lionheart) to forget about setting SP as your goal. Additionally I suggest trying an indirect method as opposed to the direct method which it seems you are trying now. Instead of lying down trying to obtain SP, just go to sleep (assuming you try on a night in bed). Just lying down and trying to project is very hard to do for your first exit. Here is what I suggest:
Go to bed on a night (maybe earlier than usual providing you can get to sleep). Have strong intentions that you will project AND set strong intentions that you WILL wake up after, say 4 hours, of sleep and remain still. This may take some practice but eventually you will wake up after the set time and you will also be aware that you should remain still. Do not move. Remain focussed and (for me at least) within seconds you will transition. You may hear noises or other sensations - ignore them and keep your focus. At this point hopefully you will find yourself ready to "exit" (although I dont like the term exit).
Another great time to try is if you have a lie in and just stay in bed, slipping in and out of sleep. You will be in purely REM at this time and if you keep it in your mind about staying still and projecting, the same situation as above should present itself.
Go to bed on a night (maybe earlier than usual providing you can get to sleep). Have strong intentions that you will project AND set strong intentions that you WILL wake up after, say 4 hours, of sleep and remain still. This may take some practice but eventually you will wake up after the set time and you will also be aware that you should remain still. Do not move. Remain focussed and (for me at least) within seconds you will transition. You may hear noises or other sensations - ignore them and keep your focus. At this point hopefully you will find yourself ready to "exit" (although I dont like the term exit).
Another great time to try is if you have a lie in and just stay in bed, slipping in and out of sleep. You will be in purely REM at this time and if you keep it in your mind about staying still and projecting, the same situation as above should present itself.