Brazilian (1st Time)

I could use some help/suggestions on how to prepare for my first time getting a Brazilian wax. Do I get everything waxed, or keep the top part (heard that area is the most painful)? Should I trim before hand (area has not been trimmed or shaven in quite some time)?

How long does the wax last (when should I schedule a follow-up)? I'm a tad bit nervous but heard this is the best way to stay clean.

Thanks in advance!!