On stock voltage I was able to get to 3.4 GHz with little trouble after that it starts needing extra anything over 3.8 needed to much voltage IMO to stay stable , but it was still with in spec until I hit 3.9 and above.
The only way to learn is to read up on it as much as you can also it is a good idea to read your motherboard manual and become familiar with the bios.
It is a very helpful guide. Overclocking is alot of trial and error and takes time and patience, but with the right knowledge its not bad at all. The Q9550 is a great processor and can take a good bit of abuse and keep going as long as you keep the voltages below 1.36 and temps below 60C the chip will last a very long time.
Good Luck and welcome to the forum