for my zombie film, I need to show the actor (me) running away from a horde of zombies that are charging at him from down the street. (Think Left 4 Dead or 28 days later, but I have slow zombies too) Are there any procedures I need to do in order to do this, or can I just film without anyone's consent?
This question is too broad.
In many cities if you will cause disruption (by their definition - not
yours) you will need a permit and insurance. In more rural areas
you don't need either. If you have a camera, a tripod and six to ten
zombies the answer is very different than if you have 50 zombies
and a full grip and lighting package. Smaller cities will have different
requirements than larger ones. Even the word "legal" has different
meanings.
You best move is to contact the authorities in the area where you
will shoot. They will know much better than anyone posting here.
Every one of us no budget filmmakers have shot in our home towns
without a permit or insurance. This might be the rare time "It's easier
to ask for forgiveness than it is to get permission." works. You will not
be put in jail, you will not be fined. You will be told to stop. That is
likely the worse that can happen.
So:
Where do you want to shoot?
How many total people will be involved?
How much equipment?
How long to you need on the location?