This, a million times (excuse the hyperbole). A low curb between the parking and bike path, and between bike path and pedestrian way is also very important. So is law enforcement that actively cites and tows cars that park on bike lanes, at least while building a culture around it.

Add to that that bike paths in Copenhagen have a totally different, much smoother asphalt. Since it is only used for bikes it lasts a long time. Cars can't drive on it because it is too slick and wouldn't stand up to the use. But it makes biking a lot easier than on rough asphalt covered in repairs, cracks ans potholes.