Custom fees between Canada and USA

What is best to do when goods are sold from Canada to USA and from USA to Canada to prevent custom fees. What about NAFTA agreement, rates, etc. Thanks for you advises.
I have heard some people write "gift" on the customs form. I do not know what the fines are to those who get caught in a lie. I paid a duty six months ago and just figured that is like paying sales tax. No big deal, probably a lot less than the penalty. I wish I knew how NAFTA worked also; and if there is a legal way to reduce or abate the duty??
Canada customs does not charge duty on US made electronic components. You will, however, have to pay the provincial and goods and services tax. The cheapest way for items coming from the States is via USPS. Canada Post charges Can$5 plus the applicable taxes. Items coming via UPS get charged brokage fees on top of the applicable taxes.
i bought a cd player from some geezer in canada and he put that it was worth $100.00 on it and there was no tax or anything---(can to us)
Thanks guys ! Turbodieselvw: How sure you are when you say that Canada does not charge duty on electronic components. Where can I check this information?
Martin - you might find something at the Revenue Canada & Customs website (not sure of web address). As Turbo indicated, you will have to pay the appropriate taxes and if shipped via USPS,Canada Post will charge you a $5 handling charge to collect the taxes. I have had a number of US made products shipped here to Alberta and have only paid the GST (the benefit of living here..) on all of the items. As indicated, avoid UPS as they have their "hidden" brokerage charge that you only find out about when the package is delivered.