I have a Nikon D3100. I'm attending a greyhound protest soon and I need help with the settings, such as ISO, aperture, and focus mode, etc. There will be a lot of people and dogs there, moving about. I prefer not to take photos using auto!
I prefer not to take photos using auto!
I understand this preference, but I think if your goal is to record this event, you should use auto. That's because the question itself indicates that you are uncomfortable with the basic exposure parameters and their use. Auto will take care of this for you — maybe not with the best possible results, but certainly with better results than using manual mode without understanding.
It's good to increase understanding by experimenting and learning, but an event you want to photograph probably isn't the time to do that, unless your goal is primarily learning and getting good results a possible nice side effect.
There are lots of valid possibilities for all of the parameters you mention; it all depends on what you want. Auto mode will generally get you acceptable middling-conservative results. Once you understand what you want different from that, it's time to dig into manual control.