This is the act of waking up after a certain amount of sleep, then going back to sleep, doing whatever technique you choose.
In the time that you are awake, there are a few things you can do, and it will probably vary depending on the technique you are about to attempt.
For DILD, you are likely going to want to read and/or think about lucid dreaming a lot, and do a few reality checks
For MILD, you will probably want to do some auto-suggestion. This is also good for WILD too, along with some visualizations and such.
Dr. LaBerge invented this technique while doing work for his doctorate. He found that among experiences lucid dreamers the addition of a WBTB resulted in 60% more lucid dreams.
WBTB Tutorial Here