Personal exemptions
When you return to Canada, you may qualify for a personal exemption. This allows you to bring goods of a certain value into the country without paying regular duty and taxes, except for a minimum duty that may apply to some tobacco products.
The CBSA has agreements with some provinces and territories that allow the CBSA to collect provincial and territorial taxes, levies and fees on goods that have a value higher than your personal exemption.
If you reside in one of the provinces or territories that has an agreement with the CBSA and you return to Canada at a port of entry in your province or territory of residence, the goods that you import in excess of your personal exemption will be subject to a provincial/territorial assessment. If you bring in more than the allowance for alcohol, you will have to pay the provincial/territorial assessment in the province or territory where you enter Canada, even if it is not your province/territory of residence.
The Government of Canada has agreements with New Brunswick, Nova Scotia, and Newfoundland and Labrador to collect the HST. If you live in a participating province and the value of the non-commercial goods you import is more than your personal exemption, you have to pay the HST instead of the GST, regardless of where you enter Canada. Effective July 1, 2010, the CBSA will likewise collect the HST for Ontario and British Columbia.
Except for restricted items, you can bring back any amount of goods as long as you are willing to pay the duty and taxes, as well as any provincial/territorial assessments that apply. This rule applies even if you do not qualify for a personal exemption.
You must always report the amount you are claiming for your personal exemption in Canadian dollars. You must therefore convert foreign currency values and any foreign sales taxes you paid to Canadian dollars at the appropriate rate of exchange.
What are your personal exemptions?
After each absence of 24 hours or more
You can claim up to CAN$50 worth of goods without paying any duties. This is your personal exemption. You must have the goods with you when you arrive in Canada and you cannot include tobacco products or alcoholic beverages in this exemption. If the goods you bring in are worth more than CAN$50 in total, you cannot claim this exemption. Instead, you have to pay full duties on all goods you bring in.
After each absence of 48 hours or more
You can claim up to CAN$400 worth of goods without paying any duties. You must have the goods with you when you arrive in Canada. Although you can include some tobacco products and alcoholic beverages, a partial exemption may apply to cigarettes, tobacco products and manufactured tobacco. See the sections called Alcoholic beverages and Tobacco products for more details.
After each absence of 7 days or more
You can claim up to CAN$750 worth of goods without paying any duties. Although you can include some tobacco products and alcoholic beverages, a partial exemption may apply to cigarettes, tobacco products and manufactured tobacco. See the sections called Alcoholic beverages and Tobacco products for more details. With the exception of tobacco products and alcoholic beverages, you do not need to have the goods with you when you arrive.
To calculate the number of days you have been absent, do not include the date you left Canada but include the date you returned. Dates matter but not times. For example, we consider you to have been absent seven days if you left Friday the 7th and returned Friday the 14th.
Who is eligible for these exemptions?
You are eligible for a personal exemption if you are one of the following:
a Canadian resident returning from a trip outside Canada;
a former resident of Canada returning to live in this country; or
a temporary resident of Canada returning from a trip outside Canada.
Even young children and infants are entitled to a personal exemption. As a parent or guardian, you can make a declaration to the CBSA for a child as long as the goods you are declaring are for the child's use.
I can't wait to go shopping down there!! 
When we went into the US last time we just kept all our receipts in an envelope so that if the customs officer wanted to know what we were bringing back we would have the receipts ready to go. Of course when we came back the girl hardly looked at us as she waved us through, gotta love canadian security 
And there is no difference between driving or flying 
