Similar to the way a RC (Reality Checks) works this can be used in an attempt to add a DC that you wish to have in your lucids. For whatever reason.

When you take an individual it is sometimes surprising how often that his or her name comes into the picture of your life.
Let's say for a hypothetical situation I would like my sister in law to be in one of my lucid dreams.
When she enters your mind. (doesn't matter why)
When she calls on the phone. Or you even see her name on the caller ID.
When she is brought up in conversation
When you actually see her. (DO a RC then or at any of these times)

But relate each of these experiences to the realm of your dream patterns.
It is likely this behavior will begin to unfold in your dreams when that person is in your dream.