In my area a chair is just a person who hands out the readings and starts the meeting and calls for a topic..or starts the reading in the liturature.
If you chair means speaking...like a 15 minite intro or telling your story, I know that the ones that help me most aren't the brilliant story tellers or speakers, but the ones who just speak from their heart in ordinary words.
I have spoken many many many years ago, and I found that i did best if i just spoke from the heart..although I usually also found myself telling myself my story in my head repeatedly for several days before

But when i started i just let er rip!