Canadian lives on USA border. Want to bring packages to USPS to ship (under $200), need customs?

[wonkavision]

Hi,

I live in Canada and I am 10 minutes for the USA. I want to bring my packages to the USA to ship. Is it true if I it's under $200.00 value for personal use there is no duty charge on most items?  

What do I need for customs...forms...etc?

I cannot find my answers on line.

Thanks