All you can do is keep trying. It took me months to learn how and they are still elusive.

My last one was strange, I could feel myself entering the LD state and then it began to fade.
I began to tense up and force it which made it fade even quicker. But when I let go, man it was like a strong current just picked my up and sucked me in.

Just try to remain passivly aware and not get too tense.