Retractable dog leashes may be great for Fido, but for folks trying to run, walk, or bike in the same space? Not so much. Keep your pup on a leash and make sure that it isn't stretched across a sidewalk, endangering others around you by forcing them into oncoming traffic or, just as bad, causing them to trip or become tangled.

Want to preserve the beauty of the season with a photo? Before you take the picture, take a second to make sure you're not standing in anyone's way.

These words of warning don't just apply to overhead bins on airplanes. When you park your car alongside a roadway that's frequented by cyclists – popular beaches and parking for trailheads, for example – check your mirrors before opening the door, lest a biker happens to be buzzing by at the same moment. (This unfortunate occurrence is known in cyclist-speak as getting "doored.")

It's always easier when bikers and pedestrians each have their own dedicated lanes. But when things aren't clearly spelled out, here’s the deal: Slower traffic should keep right, just like on the road. That means walkers and slow joggers should move over to allow runners and cyclists to pass them more easily on the left. The same rule also applies when there are dedicated pedestrian and biking lanes. So if you’re cruising along on a leisurely bike ride, for example, drift to the right to allow easier flow for speedier cyclists – and a safer environment for everyone.

When you’re out for a walk or run (and, presumably, not hogging the sidewalk) and a cyclist comes screaming past you with just inches to spare, it’s terrifying – and infuriating. Don’t be that cyclist. Reduce your speed in heavily congested areas – or avoid such areas altogether.