Default what are the setups to flash custom rom??

what are the setups to flash custom rom on MyTouch 3G TMobile whith original rom ..?
it's only by rooting at the first and flashing ?? because i found that it must also flash custom recovery ... help please..!
and how to install the custom recovery..??

my phone
Quote:
SAPPHIRE PVT 32B SHIP S-OFF G
HBOOT-1.33.0013 (SAPP*****)
CPLD-10
RADIO-2.22.28.25
OCT 21 2009, 22:33:27