I know a guy that has set a ring tone that I hear on my phone when I call him. Instead of the usual monotone ring - ring - ring as I am waiting for him to pick up, I hear a custom ringtone. Does anyone have any idea how to set this up?

This sounds like something the carrier offers.
Why don't you ask this guy?

For $1.49/mo, Tmobile has Caller Tunes. Other companies probably offer something similar.

"CallerTunes® is a cool, new service that lets you choose what your callers will hear until you answer your phone. Instead of the normal, boring "ring, ring" they hear today, your callers can hear music, sound effects, or short, spoken clips."

Wirelessly posted (8320 Curve: BlackBerry8320/4.2.2 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/100)

Cingular and verizon both offer this under differebt names abd differebt prices. Others might too.. But I'm positive about those two