As of 1/24/2008 a U.S. Passport is not needed until June of 2009.
Tips for crossing the border. First of all do not be nervous Canada is not communist country. Try to allow only one person to answer the questions otherwise the border person and yourselves get confused and it gets frustrating.
If you have on sunglasses please take them off and look them directly in the eyes.
There are a three restrictions, Potatoes, Blueberries and Firewood. Potatoes are not allowed fresh. You can bring them across already cooked, frozen, canned, or boxed.
If you are using nightcrawlers for bait make sure that they have been in worm bedding or newspapers for 2 weeks prior to your trip.
Any adult over the age of 19 is allowed to bring into Canada with no duties either 1-1liter bottle of booze or 1 case of 24-12oz beers, or 1 gallon of wine. With tobacco products you are allowed 1 carton of cigarettes, 1 box of cigars, and 1- 200 gram package of tobacco.
If you are traveling with children please have a birth certificate if both parents are with the child and a notarized permission slip if only one parent is present.
There are also restrictions on certain foods that are above and beyond what most people would use in a month.
If you are a felon and they run your license at the border there is a good chance that you will be denied entry. You can check the Canadian website for more information.
What I have been told is that if you have a DUI that is older than 5 years, you can come into Canada. However if you have multiple DUI's there could be a problem.
Following the above items can expedite your safe and uneventful crossing of the border.
If you get someone that you feel is out of line or really obnoxious you have the option of asking for a supervisor. I have been told this several times. If you have any other questions feel free to ask.