I would really like to volunteer/observe at nearby lab, so how can I? What should I do so they’ll say yes? How should I contact them? What should I write to †hem?
THANKS ! 
Yes write a short polite email telling them why you are interested
My son attached a PDF resume to a relatively short email about his specific interest in that professor’s research and relevant coursework and experience. He asked if he could come in and talk about doing summer research, rather than asking for the position outright. He sent it a second time a week later after no response, and did get a “Sure come by and coordinate with the person CCed on this. Thanks for being persistent; I was in Europe last week.” He’s working there twice a week after school now and more in the summer, so it can work.
You’ll probably have to try multiple professors, of course. Try larger labs, because they may have people with the time to supervise you a bit.
It looks like you are an 8th grader from other posts. Depending on the field, you’ll probably have to wait for volunteering. For example, I’ve heard that there are some liability things for kids under 16. And, there is relevant coursework to think about.
Just observing for a few days should be easier to get than volunteer research. See if your parents have any connections to a lab that interests you.
@sgopal2 @Ynotgo THANKS!
Here is a really useful document I found awhile ago: http://oso.stanford.edu/files/programs_111.pdf