Ya I agree with Ubik. When I try to LD I often experience SP, too. 3-5 times a week usually. Experimenting with it gives you a really good feel for it. I learnt how to make the SP last longer but it's kind of hard to describe. Like in a lucid dream, you would not keep an empty mind but rather keep the input/output of the REM system going to experience the SP more as a type of LD that you don't wake out off. This also gives you several tries to induce LD/OBE. I manage a minute or two by just keeping all the sensations going, imagining stuff, trying out sensations etc. Also visual halluscinations could lead you to an LD if you focus well enough and just kind of "dive into" the dream you might be seeing. But Ubik's method and related ones are usually better since you're basically already in the dream and shouldn't need the circuit of imagining a dream etc.