How do I overclock my system?

Specs are as follows:

Asus P5K Motherboard
Intel Core2Duo E6850
Gigabyte HD 5450 (<-- huge piece of shit if you ask me, but I'm a poorfag)
2x2GB of DDR2 667 Ram (Aeneon AET860UD00-30DC07X)

I have a Scythe Ninja on my CPU, it's at 20-25°C when not under heavy load, not going above 33 when I'm making it sweat.

Also, would overclocking help me, or will the system still be worthless because of the VGA? (I use my system mainly for gaming. I don't edit videos or whatever.)
Thanks in advance.

(Pic unrelated, I just looked for something colourful to catch your attention.)