If you haven't already read this, the Overclockers.com Beginner's Guide Section has some good stuff to know about how to overclock, and other helpful hints about your computer in general. One article I think is definitely worth a look is this one , which was written by one of our Forum Senior Members, Batboy. It is a very thorough article that gives you the do’s and don’ts of overclocking. Likewise, you might find the CPU Database of some help in determining what others have been able to safely overclock your processor to. The following is basically my own sumation of what these articles say... but don't overlook the articles, either.
Take baby steps... nothing more than maybe 135FSB on your first shot. Boot into Windows and run some sort of processor intensive application or burn-in utility for about an hour, and if it's stable, reboot, and try a higher FSB. Basically, this is trial and error. If you go too high and the system will not POST, you must find the "clear CMOS" jumper, and set it so it will clear the BIOS (your manual should have more info on this). This will restore everything to default, but it should let you boot.
You'll want to keep an eye on your temperatures. Make sure they never exceed 50C, and try to keep them below 45C.
If an overclock is somewhat stable, but still gives you some errors, you can boost the voltage, but then keep an even closer eye on the temps as that will raise heat.
Some good programs for burn-in and general system maintenance are Motherboard Manager 5 (MBM5), SiSoft Sandra, Toast, and Prime 95. You can check to see if some of these are available at downloads.com (I know Sandra is available there), and aoafiles.com also has some good CPU programs (and other nice, interesting stuff, as well).
G'luck, and report back with your max. speed and/or any problems you may have!