I've heard all sorts of confusing input on this. One minute people say the newcomer is the most important person in the room. Then one of them shares, and the next minute someone is talking about taking cotton out of their ears and putting it in their mouths.
one sponsor says keep quiet until 30 or 90 have gone by, another gives their sponsee the assignment of sharing at their next meeting.
I've sat through many meetings where the entire discussion was whether or not newcomers should share.
I found the endless arguments over it way more distracting or detrimental than any share by any newcomer.
My feeling about shares is if you have something on the subject that you feel you need to say, speak up. Keep it under five minutes (three is even better) unless it's critical to keep talking. Nearly every share has something to offer at least SOMEONE else in the room. Every old timer might roll their eyes over something a newbie says, but there will be some other newbie in there thinking "hey, someone here DOES feel like me! I'm in the right place!"
In a step study or literature meeting, I think it's good to stay aware of our experience level and rather than a newbie sharing "advice" on a step, ask for clarification, mention where they are struggling, or admit they don't understand how to apply it.
Sponsors can usually offer good feedback to a newbie on the nature of their shares.