To cross you need to fill out the 7523 with the proper tariff codes & country of origin & whatever else is on the form. Country of origin is where the item is manufactured not where you bought it. Some things also require extra documentation before being allowed entry. It depends on the item as to what else is needed or if it's allowed at all. Research before you go.
Some items just lend themselves to extra scrutiny or hassles from the border guard. Some on here have reported being hassled.
https://forms.customs.gov/customsrf/getformharness.asp?formName=cf-7523-form.xft
http://prototype.usitc.gov/tata/hts/bychapter/2005_supp.htm
http://www.usitc.gov/tata/
You also have to pay the commercial fee which I believe is $10 per trip or you get an annual sticker for $300. There was a time when they let us through without it but they told us if we go once a week we had to get the sticker, so we did.
When you find doing what's right hard to do - you've got a problem.