This should be your first stop.
Core2 Overclocking Guide (generic)http://www.tomshardware.co.uk/forum/259899-11-core-overclocking-guide
Next stop should be a guide for your particular motherboard. Google is your friend.
Also look at 680i OC guides. The 750i is just a 680i modified to be compatible with the Yorkfield quads. I used this one with my old 680i eVGA board:
680i overclocking guidehttp://pc.ign.com/articles/747/747606p3.html
It's pretty good except for the section on memory settings. Unlink your RAM and set your memory frequency to twice the FSB frequency or 667 MHz.----------
Overclocking since 1978 - Z80 (TRS-80) from 1.77 MHz to 2.01 MHz