There are a few tricks I use... but I don't recommend the experience (It can be... uncomfortable {there is a reason you don't remember the point you loose consciousness}).
I don't know if these are universally applicable tricks either. But focusing on a point (visualizing it as actively as you can) seems to be important to staying awake through the process of falling asleep...
I’ve only noticed one other side effect. I normally experience hypnogogic jerk and since starting magnesium, a few times the jerk itself has pulled me out of the descent into sleep.
But having actually followed the process, I can now understand how it can help with lucidity.
Usually Wake-Initiated Lucid Dream involves remaining completely static, to make your body believe it's sleeping. Never worked for me.
When your body locks up, test it. try to use as much force as you can without 'breaking' that lock... it keeps you in the present moment and 'close to being able to move'...
The standard: focus on your breathing is also applicable.
What has helped the most is imagining a dot, and moving that dot around, changing its color, moving it along the z-direction (closer). Focusing your mind on that keeps it active.