How to quick-scope for beginners in Modern Warfare 2?

I love to snipe. I do quick-scope matches with my friends on Xbox but I suck. My friends always kill me and I barely get to kill them. I need to know the best guns, equipment,perks and settings to use to quick-scope like a pro! How do I practice? How would I use my quick-scoping skills in an online match where nearly every one uses machine guns? Please help!