<p>Another thing, mj93, is to go into your geometry textbook and to do some additional problems (especially problems that relate to triangle similarity). Visualization isn’t just about 3-D visualization - a lot of it is also about superimposition (can you superimpose a triangle on top of another, or can you superimpose two sine/cosine waves on top of each other?) You have some very good questions - I posted a thread about that 2 years ago, though it was met with only 2 responses. There are some really good chapters that require a lot of visualization - the Maxwell’s equations chapter in physics textbooks (they give you an intuitive feeling for them, though they don’t develop them rigorously) require superimposition on top of 3-D graphs. </p>
<p>I also think that videos could help you with visualization (especially since they often draw out the visualizations for you). I don’t know of any particularly good educational videos though, since I tend to prefer studying out of textbooks.</p>