How do you find main points in the textbook and passage? Do you have to copy them from the textbook and passage? Or do you write them in your own words?

When looking through a textbook, you should try to distinguish what are examples/diagrams and what are definitions. Examples are helpful however definitions are usually the main points. So what I usually do is write down the definitions (try using your own words if possible, but if you can't then that's okay too as long as you are writing it down somehow) and if I think that topic is particularly difficult to understand, then I'd also include the examples and diagrams.