Protest Basics?

I'm planning to attend the march in DC on January 13, and I need some advice both on what to expect and how to prepare.

I am not a stranger to protests. I attended a few during the George Floyd uprising, some of which were quite large, but I have a feeling this one will be more massive than any I've participated in before. With that in mind...

What are the most common threats protestors will face? What steps should I take to ensure the safety of myself and others? How do we defend ourselves from cops, counter-protesters and other aggressors? Are there essential supplies or tools I should bring to this end? Is there anything I should not bring under any circumstances?

Are there any environmental hazards I should be aware of? How do we avoid them?

Are there conventions and strategies employed in very large protests that I should be aware of, so as to more effectively coordinate my efforts with those around me?

What are the tactics and methods of disruption used by cops and others looking to disrupt the march? How do we counter them?

How do I identify plants, saboteurs, and other state operatives? What steps, if any, should I take to expose them?

Will my ability to reach the protest be hampered deliberately or incidentally if I need to drive several hours to the site of the protest? Are there any legal ramifications to moving out of state to join a march?

Is there anything I have failed to consider?

Thank you, comrades, for any advice you can muster.