Regarding walking on left or right, if there's no side walk, and especially when the road is not very wide, it's safer for pedestrians to walk on the left because they are able to see upcoming vehicles on their side. If they walk on the right, cars coming from behind, the drivers cannot make eye contact with the pedestrians.
If the street has side walk, it doesn't matter left or right. Pedestrians can walk on either side.
For mix-use trails (walking & biking), although many people choose to walk on the right, I think it still makes sense to walk on the left, since you'll see oncoming bikes on the same side. Bikes don't have noise like cars, so it could be a big problem if you don't notice them approaching.
If the street has side walk, it doesn't matter left or right. Pedestrians can walk on either side.
For mix-use trails (walking & biking), although many people choose to walk on the right, I think it still makes sense to walk on the left, since you'll see oncoming bikes on the same side. Bikes don't have noise like cars, so it could be a big problem if you don't notice them approaching.