Don't drive to the site. Use a bus instead. Cops will cerainly be writing down licence plates. You could drive somewhere further away from the site and go from there.
If anyone tries to argue for violence, they are probably a plant and you should isolate them.
Take scarfs and plenty of water in case of tear gas.
Do not wear an expensive watch and use a cheap alternate cellphone, because pigs will certainly rummage through it if arrested (and will probably be interrogating you for the lock screen combination).
Have an emergency contact and shelter in walking distance, so you can go there in case of pigs going berserk, until things blow over. It's better if you travel as part of a larger group for this purpose. Someone will know someone.