What timeline should I be looking at?

Complete noob here, so bear with me.

I've just started my first year at Georgetown, which seems to be a decently placed uni according to some posts on here. I have a few questions about how to maximize my chances of success in the future.

E.g. is it necessary/recommended to do anything in the summer at the end of my freshman year? What's the best course of action to take, and when do I start doing applications/reaching out to people/reading books etc? Is it already too late ??

Same questions for the end of my second year: should I apply for a SA position? Or is this just for juniors? How else can I try boost my chances to actually get a SA position in at the end of my junior year?

Any advice would be much appreciated thanks x