This processor can be overclocked to some degree without any extra cooling (assuming you have the stock or better cooler and decent airflow). The general approach is to enter the BIOS and lower the HTT, RAM, CPU & NB multipliers to their lowest settings then increase the bus speed until you wont boot. Then increase the multipliers back up and lower the bus speeds til it boots again and see if it's stable. You will probably need to increase the voltages to gain stability.
Watch the temperatures while overclocking: I would not want to exceed 75*C load on that CPU.
For a more detailed explanation, I would look at guides such as:
http://www.overclock.net/t/307316/offical-overclocking-guide-amd-socket-am2