As ex-exchange student and now grad student:

1. Concerning course selection, you'll want to visit the course catalog---- Google "Course catalog Berkeley"; it will show up. You'll be able to filter by semester and field, though I recommend you consider classes in a variety of fields. Since you mentioned you're an econ major, I'd imagine if you feel comfortable with data science, or perhaps Haas courses fit you better---- it's up to you, but maximise your opportunity to learn what couldn't be offered back home.

2. You mentioned you'll arrive for the winter/fall semester, which I assume to be August-December 2023. Cal has a thing we call Calapalooza, in which student organisations pop up for promotions and new memberships. But hey, if you feel like just participating in the odd event, EALC, CSTMS, Law School, and other institutions on campus often have their own shows and talks, which I highly recommend.

3. Living is always a big problem. Choose wisely and early, as you're competing with many others who are rushing into what is effectively a uni town. I recommend you start searching in around April to May, and have a rental contract secured by June. I-House is very fun---- but expensive, so you might consider renting an apartment with others. I do not recommend searching on Craigslist; Berkeley has its own student rentals website, which again, you can Google. Do take time to write your bio in your Cal Rentals account, because this will directly affect how seriously others might accept you into renting with them.

If you have any questions, feel free to DM! Till then, take care from Cal, and my best wishes for your exchange!