I am often asked this question by newbies and others looking to enhance their LD likelihood. Frankly, I had never given massive thought to it, other than the fact that I like to engage in a repetitive ritual, to let my mind know it's LDing time. But invariably, people want to know "should I read about lucid dreaming" or "should I visualize getting lucid in my next dream" etc ...
I do believe and have always believed that setting a few goals and locking them in your mind before returning to sleep is crucial. But that says nothing about how to spend your 45 minutes or so before hand.
Lately, I have been changing things up, due to some general concerns about insomnia. Basically, I was meditating, lights out and just trying to maintain a sleepiness. I did not want to wake up too much. This was seeming to have a negative impact on my dreams in general.
Then I went back to my original protocol which had me simply going to my on demand cable area, and watching some free music vids during my WBTB. Mostly metal and hard rocking stuff. But what is this type of music? Well, it's creative. But it's also technical. It's simultaneously right brain and left brain on a certain level. Plus, I still enjoy the hell out of it.
So ... I wonder if activities that exercise both areas of the brain in some sense make for a good WBTB activity, to facilitate coming lucidity? Hmmmm. It does kinda seem that way.