You really need to read some overclocking guides.
I'll give a brief overview.
Raise the fsb until prime fails, then raise the volts until it passes and continue raising the fsb until you reach the point where either volts are too high (>1.55) or temps are too high (>55). Then back off the fsb a touch and run prime95 for several hours to make sure its stable.
Before you start overclocking you must make sure that the ram is on a divider such that it won't go above 200mhz, use cpuz to check this. You must also make sure that the htt doesn't go above 1000mhz by lowering its multi to 4 and then 3 at 250fsb (4 x 250 = 1000).
You will have to keep checking both the htt and the ram as you raise the fsb to ensure neither exceed their limit.
Edit: Sorry, thats aimed at A64 overclocking. I'll leave it there as i expect the basics are the same. Max voltages and temps are probably different, i have no hands on experience with socket a athlons so i'm not able to help.