For current info go to - Tips for Travelers to Canada
Note the requirements for air and land travel are different today.
What is required and what gets checked are two different things. You better have what is required. I have gone in and out of Canada multiple times with only a drivers license or no ID check. Went in Canada, with my Airstream and dog, last year and had three questions at the border 1. Where do you live, 2. Do you have any firearms 3. What do you have with you. And was waived on through. No ID check, no vet paper check took about 15 seconds, plus 20 or 30 minutes in line. Went on to Alaska and upon reentering got a long list of varied questions, was asked for photo ID and proof of citizenship (passport or birth cert). Just had my driver license ready, passport was in the trailer. Oh man that upset the border guard, gave me a lecture about not being prepared, asked why I wasn't prepared, related my previous border experince, he got more upset (I was polite really) had me pull in to secondary. He explained proof of citizenship had been required for his entire 30 years and a drivers license did not meet the citizenship requirement. I got the passport out in secondary trusck and trailer searched and was on my way. This was the first time I needed more than a driver license. About 20 minutes for that crossing.
I got beef and other food yanked entering the US. Look at the restricted items list before crossing either way.