First of all, you must understand and remember the basic knowledge of books, such as theorems, axioms and conclusions derived from correct axioms. Memory is an effective understanding, which is the most important thing. Geometry is actually reasoning. I think the best way is reverse thinking, that is, reverse deduction. General geometry problems will give you some conditions, so that you can draw conclusions according to the conditions. According to the conclusion, you can push down the conditions that need the conclusion to be established, and then see if the given conditions are met. If they are met, you can push forward. If it doesn't meet the requirements, it may be insufficient. You may need to add auxiliary conditions, such as adding auxiliary lines.