Internet restrictions

[#1]

Hi,
I have a 10GB download limit on my account every month. If I go over, I get charged, so I want to try to reduce the amount of info I download whenever it gets close to this limit. The main things that eat up my bandwidth are streaming videos/programs and sites with lots of pictures, such as Facebook.
I know how to turn pictures and streaming off at the browser for my laptop, but I'm not the only person that connects to my Wireless connection. Is there a way that I can restrict this information for everyone who connects to my modem, without having to access their individual computers?
I have looked in control panel but I don't want to start clicking on things in case I mess it all up!
Any help will be highly appreciated.
Thank you! 

[#2]

The only real way of controlling what everyone can access over the internet is to configure a local proxy server which all internet access will pass through before getting to your router.
Realistically unless you have a resonable understanding of how to configure proxy servers and router restrictions you are better leaving everything alone and just shouting at whoever you suspect is using more than there share of bandwidth.