The easiest way is just to apply an above-standard FSB (i.e. >133MHz). The alternate method (although these can be combined) is to unlock the multiplier on the chip. The 1500+ chip attains it's 1.33GHz from a 10-times multipler (10*133=1330). That ratio is locked onto the chip. By rejioning the L1 bridges you'll be able to choose the multipler that is applied. Both this and the FSB are varied in BIOS.
There are many, many threads on this topic here - so I won't duplicate.
Do it - just make sure you have adequante cooling. Remember, that there's no reason your chip should overclock. Most do, and some very well indeed. You'll only know by trying.