This is a great question, and I sure hope that one of The Chrises (plural of Chris) or Jackie, or Deb, or some other fabulous WBT Intern or moderator answers this question.
Now, as an ESL certified teacher myself, this is how I would answer this question. (And if I read something later in an Ebook or find a better answer, I will post again.) But consistency has definitely worked for me with my ESL and non-ESL students. In fact, giving those super important vocabulary words their own gesture helps them understand how to use it and why it's so important to whatever we are studying. In fact, months later, my students still remember the different gestures for the many...many....MANY vocabulary words. And what really motivates them is when they come up with the the gesture themselves, or even when a class leader makes it up, they would rather use their peer's gesture than something uncool that I come up with.
Now, if you want to make sure your students chunk question words together, like the five W's, maybe come up with a gesture for the "5W's" and then precede with the individual gestures for these words. What is so special about Why and What? What do your students need to know about these words to use them properly? Ask them to make up a helpful gesture for them to remember the meaning and correct usage of this word, so they will know how to use any of these vocabulary words in meaningful ways.
For instance, in fifth grade science, earth science is where my class struggles. I chunk some physical features of the earth and the processes that form them into two categories "destructive forces" and "constructive forces." Both categories have a gesture, and that makes it easier to review the different features and processes that form them. Does that make any sense?
You're the expert for what your students need to know. So go with your gut, but consistency in any area usually leads to good routines and success! And it's just fun to watch them do the gestures when they're working independently and they don't know you are watching!