I prefer to see speed limit signs as a suggested minimum, except where actual hazards are apparent.
...At stop signs, the regular rules apply unless no one has entered the intersection within 3 seconds. That must mean its my turn!
...and a bureaucratic "no" really means "we're trying to eliminate 85% of the population that will accept that answer." In this situation, I find deafness convenient.

I'm considered a pretty straight and narrow kind of guy, but there are some suggestions I tend to ignore.

Changing my oil at 3,000 miles? not a chance.
Don't eat after swimming? whatever.

Real rules like speed limit I tend to follow. Laws about drugs and other laws that many people don't seem to care about I follow strictly.

I change "rules" in a way that makes me feel karmically (is that a word?) balanced afterward. Not in a selfish way, but not in a stupid way either. I go through line at the supermarket to buy 3 trays of sushi at $7 a piece and only one of them rings up. I tell the cashier - honest mistake. But if that cashier doesn't do it right because he's not paying attention because he was rude to me and busy talking to his friend instead? Tough break, dude. Free sushi for me.

Or the time at a nice restaurant with a nice waitress, we got the bill and discovered that my wife's clam chowder had not been added. Do I call her over and tell her the mistake, and volunteer to pay more? Or, if I don't, will she get in trouble and have to answer for it out of her paycheck at the end of the day? I solve the problem in the way that makes me feel good -- I add the cost of the chowder onto the waitress's tip. I don't waste time waiting for a new bill, I paid for my food, waitress doesn't get punished for her mistake.

And so on. I probably hit a handful of those moments every day.