A fellow safety speaker who was starting out in the speaking business asked me if I would critique his style. “Sure, I said, send me a video.” He had a charming style, connected well with the audience, had a wonderful closing poem (which I recommended he memorize rather than show on slides and read) and overall has the makings of an excellent professional speaker. 
Only one thing stood out that needed refining. He asked the audience to raise their hands several times without a need for it besides just getting some people to send a signal. There’s nothing wrong with getting your audience to raise their hands in response to a question or statement as long as you follow these two “rules.”
1) Don’t do it too often. I don’t know exactly how many times per hour that is, but anything over three or four times is pushing it.
2) Do it for a reason. I heard a speaker ask “how many of you here like to laugh?” Really! Everyone does. Now, if you are making a funny point such as asking “who here hates to laugh?” and if someone raises their hand you kindheartedly pick on them. (That’s a tricky tactic that requires practice and experience because it could backfire.) then it makes sense. But just to ask questions only so you get people to raise their hands is lame.
When I give my “Misconception” test I ask for a show of hands related to how many incorrect answers you circled. I give a broad estimate of how many hands go up (“I’ll ask “How many of you got four wrong?” After hands go up. I’ll look around the room and say something like “It looks like about 60 of you got four wrong.”) So, I need to see a show of hands to prove the point that we all have misconceptions. (When giving the test is the only time I ask for a show of hands more than two times during a talk.)
You may have a valid reason to get folks in your audience to raise their hand without actually estimating, or even recognizing, how many hands go up, but I doubt you have more than three or four valid reasons per talk.
KEEP THE LIGHTS ON! Third Common Mistake Amateur Safety Speakers Make
DON’T GO OVERTIME! Second Common Mistake Amateur Safety Speakers Make
YOU NEED TO USE A MIC! First Common Mistake Amateur Safety Speakers Make
