I think 'shizukani shiro'? I hear that one a lot. I mostly hear 'urusai!!!!', though, which means 'noisy' or 'too loud', but implies 'shut up!'... Others will know more than me, though.
And by the way, no, those are not said to me!
*Edit* Whoa! That's what a phone call will do to you. Everyone beat me to it while I was in the midst of replying!
I'm guessing you want to say it because someone is being annoying and such.
"Urusai!" would fit. Pretty much it is telling the person to shut up.
If you are really looking to get into the language by the way, let me recomend you the book that I started on. You should really take a college level class if you want to learn, but this book is cheap, and one of the best I've seen so far. At the very least, you can get the basics done and learn some of the writing. You'd have a huge leg up before the class might start.
Damare!! Is my personal favorite =P
However on a politer note, I think my friend told me that you can say "shizuka ni ite kudasai" or "shizuka ni shite kudasai" I forgot which one he said would be better to use. Any help on this one?