1. It will depend on your motherboard how (and if) you can overclock it.
2. Try Google (on overclocking) - there's lots of sites.
3. Remember you're likely to get problems (eg, your operating system won't boot), if you overclock too much.
4. I doubt you'll be able to notice the difference (I don't mean measure it, but see it) after overclocking.
Good luck.