Entering Canada from USA by car: is there checkpoints or can you come & go as you please?

Do they have checkpoints all along the Canadian border or is it easy to just enter and leave? Once you enter do you have to register somewhere? I don't want to bother renewing my passport if I can help it. Can I just enter with a USA driver's licence (it is our national identification card here) if I'm just spending a month or so vacation?? Thank you.