To finalize the transition into the dream, I will normally try to vividly remember a recent memory. I try to make it a memory that involves touch and movement, so my body will be engaged with my environment. I find that a memory comes easier than an invented scene, but you can use either one. The trick is to just nudge some sort of dream to begin, and then go with the flow once it starts to take over. Try to engage with whatever scene or narrative materializes.