Q9550 790i FTW

Read these:
HOWTO: Overclock C2Q (Quads) and C2D (Duals) - Guide v1.6.1
http://www.tomshardware.com/forum/ [...] uals-guide

Core 2 Quad and Duo Temperature Guide
http://www.tomshardware.com/forum/ [...] ture-guide

After that, google something on how to OC your particular motherboard.

Then, here's your problem:
These are guides, not cookbooks of detailed instructions. So you need to be familiar with what they are talking about. There are so many variables that what worked for someone else may not work for you.

Intel has both "recommended maximum" and "absolute maximum" temperatures and voltages for their CPU's. Having said that, it is pretty difficult - but not impossible - to fry a moderm CPU. They tend to throttle back their speed or thermally shut down before damage to the CPU occurs.

Hate to tell you this, but you have some homework to do. After that, come back with definite questions.
----------
Overclocking since 1978 - Z80 (TRS-80) from 1.77 MHz to 2.01 MHz