Around here the crews do a pretty good job plowing, including the bike lanes, so I just ride more or less normally. In general I try to give cars more clearance at a few tight spots. For instance at one left turn from a divided highway I normally will cross over and hug the left shoulder leading up to the turn. When conditions are snowy or icy, I don't do this. I keep right until the intersection and then stop and cross during a clearing.

In general, I recommend evaluating each danger spot on a case-by-case basis and doing whatever you feel is safest. No need to adhere to any fixed set of rules, because every situation is different.

Plows haven't been a problem for me.

On a normal 45 minute ride, I've found I need an extra 15-20 minutes riding time on snowy days. Maybe 10 minutes extra on icy days.

I think the most dangerous time is the first snow of the year, when drivers are still getting used to the conditions.

Paul