Not familiar with that motherboard, but the concept for OCing is the same for most systems.
You'll want to set your RAM ratio to 1:1, which means for a Q9450 @ stock, that would be DDR2-667.
Make sure it's set to its rated voltage & timings.
This keeps the RAM from potentially holding anything back initially.
I'd suggest disabling C1E/EIST in your CPU features for now.
Then increase FSB gradually, testing for stability as you go.
Obviously you'll eventually need to increase vcore at some point along the way.
Unless temps get too hot, i'd say start @ 1.25-1.3v for CPU voltage.
Once you reach higher FSBs (usually 400+, depending on mobo), you'll likely need to increase MCH/NB voltage & VTT voltage to maintain stability.
Some tools to check for stability:
Prime 95 (use small ffts to test CPU; large to test mobo/RAM; blend for overall system)
32-bit version
ftp://mersenne.org/gimps/p95v2511.zip
64-bit version
ftp://mersenne.org/gimps/p64v2511.zip
LinX
Set to all RAM for performing a very heavy stresstest for the CPU & RAM
http://www.xtremesystems.org/forums/showthread.php?t=201670
HCI Memtest
Don't worry too much about this right now; it's primarily for testing RAM stability, but also stresses the MCH/NB heavily.
http://hcidesign.com/memtest/MemTest.zip
Memtest86+ v4.00
Burn to bootable disc & run for memory error checking
http://www.memtest.org/#downiso
CPU-Z
Tells you CPU/RAM speed; vital tool for any overclocker
http://www.cpuid.com/cpuz.php
RealTemp
Tells you CPU temps/CPU VID/etc
http://www.techpowerup.com/downloads/SysInfo/Real_Temp/